There is an "alarming" shortfall in the number of Foreign Office (FCO) diplomats able to speak Arabic or Russian, MPs said as they warned against potentially "disastrous" future budget cuts.

The Foreign Affairs Committee said the "strongest criticisms" they had heard from witnesses about the FCO's language abilities were for regions where there is "particular instability" and the greatest need for expertise.

The committee recommended that FCO budgets should be protected in the next spending review, stating that the cuts already imposed on it had "gone beyond just trimming fat".

The cross-party group of MPs said criticism of FCO expertise had centred on an apparent decline in proficiency in foreign languages.

Former Labour Foreign Office minister Lord Malloch-Brown told the committee in 2012 that language skills were "in crisis" and former ambassador to Libya Sir Oliver Miles saw it as "deplorable" that "too many positions" in North Africa and the Middle East were held by non-Arabic speakers.

The committee's report said proficiency in Russian "is also seen as a weak spot" at a time when tensions with Moscow are high over the Ukraine crisis.

"It is alarming that the strongest criticisms that we hear about FCO capability relate to regions where there is particular instability and where there is the greatest need for FCO expertise in order to inform policy-making," the committee said.

"We also note that the percentage of 'speaker slot' posts occupied by someone possessing the specified level of proficiency in the required language ... is currently just 38% overall, and in the same key regions it is lower still: 28% in FCO posts in the Middle East and North Africa region, and 27% in Russia and Eastern Europe."

The FCO's senior civil servant Sir Simon Fraser "readily acknowledged that the low levels of target level attainment in foreign languages were unacceptable and said that heads of mission and FCO directors had been given 'very clear instructions' that people should be given time to do their language training and were given strong incentives to do so - both carrots and sticks".

The MPs said they were "heartened to see that the permanent under-secretary has gripped the issue and has made a clear personal commitment to reversing the trend".

The committee urged the next government to resist the temptation to impose further cuts on the FCO's budget, warning it could have "disastrous and costly" consequences.

Cuts imposed by the current Government already mean "capacity now appears to be being damaged", the MPs said, and a further spending squeeze would reduce the UK's diplomatic influence.

Committee chairman Sir Richard Ottaway said: " The cuts imposed on the FCO have been severe and have gone beyond just trimming fat.

"Further cuts would mean a reduction in the UK's diplomatic imprint and influence, and the FCO would need to aim to do less.

"The FCO's budget is a tiny element of Government expenditure but it makes a disproportionate contribution to policy-making at the highest level, including decisions on whether the UK should go to war.

"Impairing the FCO's analytical capacity for the sake of a few million pounds could be disastrous and costly. The next government should protect FCO budgets from any further cuts."

The MPs also said that the value of UK exports of goods and services was £506.5 billion in 2013, "significantly lower than where the Government would have expected to have been in order to meet its £1 trillion export target by 2020".

The target should be axed and replaced by a "more realistic" goal, the MPs said.

The committee also recommended changes to the way events at embassies were sponsored by businesses, claiming that the amount of money currently being received did not justify the risk of negative publicity.

The FCO disclosed £271,500 of commercial sponsorship at overseas posts in 2013/14, with parties to celebrate the Queen's birthday proving particularly lucrative events - the department received more than £188,000 for 10 parties, an average of nearly £19,000 per party.

" The FCO needs to consider carefully the accusations that the dignity of the department has been jeopardised by seeking commercial sponsorship," the MPs said.

"We acknowledge the force of argument that sponsorship could amount to, or be perceived as, an attempt by outside organisations to 'buy' influence of the FCO."

They said there could be "appreciable public benefit" from commercial sponsorship through reducing the burden on the taxpayer and promoting British industry.

But they added " the value of sponsorship currently being raised by the FCO hardly justifies the reputational risk to the department, nor does it appear to compensate adequately for the undoubted value that sponsors receive on behalf of the taxpayer".

They urged the FCO to get more money from sponsorship deals and publish details of all agreements, not just those worth more than £5,000, on a rolling basis.

The MPs also criticised the FCO's "disappointing" performance in promoting women to top roles.

"In the history of the FCO, no woman has ever held a post at the highest grade," the report said.

"The problems may not reflect institutional barriers but rather a lack of confidence among women that they have the same opportunities for career development and advancement as their male colleagues."

An FCO spokesman said: " The FCO has had to play its part in reducing the deficit and this has meant some tough decisions to help get the public finances back on track."

He added: " The Foreign Office has a renewed focus on languages as a diplomatic skill and in September 2013 we opened a new language centre to strengthen our training programme in key languages including Arabic and Russian.

"All heads of mission in Arab countries speak the language that's used to do business in that country; 76% speak Arabic and the other 24% speak another local language. We would not send an ambassador to a country without the appropriate language skills if they could not effectively conduct business on behalf of the British Government."