The company reported a surprise jump in bottom-line profits to £171 million over the past six months.

This compares with a £55 million loss last year, and was boosted by better-than-expected performances from its Post Office branches.

Last night MPs on an influential Commons committee urged Royal Mail to think again before deciding whether to push through the stamp price increases next April.

Adrian Bailey MP, chairman of the Business Innovation and Skills committee, said that the company should "look again at the proposed increases".

He told The Daily Telegraph: "These figures are much better than we were given to expect and call into question the need for the scale of the price increase that they are going to implement.

"They should look again at the proposed increases. In the light of these profits, Royal Mail should re-examine their pricing proposals given the fact that people are suffering high energy bills and petrol bills."

A spokesman for the postal watchdog Consumer Focus added: "Royal Mail is going through major transformation, including modernisation and operational changes, as well as changes to its regulatory regime. This mustn't divert attention from the fact it delivers an essential universal postal service which needs to be affordable and reliable."

Ofcom, the postal regulator, is considering allowing Royal Mail to hike the price of second class stamps by an unprecedented 50 per cent, and remove the cap on first class stamps.

The proposed seven-year deal would see the cost of a second-class stamp rise from the current 36p to between 45p and 55p.

There would be no limit on the price of a first-class stamp, which currently costs 46p. One option could be to bring it more closely into line with countries such as Denmark, where a first-class stamp costs 67p, or Italy, where a next-day delivery costs 69p.

Royal Mail normally sets its increases in stamps every December for the following April. The company is now likely to wait to see the outcome of a consultation on Ofcom's proposals before deciding prices of stamps for next year.

Royal Mail said while its financial performance "is beginning to improve, we have a great deal to do still to return Royal Mail to sustained financial viability".

In the half year to 25 September, Royal Mail's group revenues increased by £200 million to £4.6 billion.

However the number of letters fell by 6 per cent to 59 million items delivered daily, the lowest for around 20 years as more people rely on email to communicate.

Losses in the UK Letters business narrowed slightly to £41 million. Royal Mail said: "Were it not for profits from its GLS parcels business £58 million and the Post Office Limited £55 million - the group overall would have made a loss".

Cost-cutting continued at the company, with 5,000 people losing their jobs over the past year, nearly 2,000 of them from its head office or other managerial roles, reducing the Royal Mail's workforce to 163,000.

Royal Mail said it was "vital" that the European Commission approves a plan for the Government to take over pension deficit, which is heavily in the red, allowing Royal Mail to be privatised.

Moya Greene, the company's chief executive, said "painful changes" remained to be made to secure its future, including increased automation and more mail centre closures.

She said: "Our focus therefore remains on returning to sustained financial viability. We will continue to reduce our costs wherever possible without compromising the six-days-a-week service.

"We look forward to working with Ofcom to secure a new regulatory approach as the need to do so is pressing.

"Furthermore, it will be essential for Royal Mail that the European Commission approves the Government's state aid application to relieve the company of its historic pension liability and allow restructuring of the Royal Mail balance sheet."