Ministers are set to postpone plans to part-privatise the Royal Mail after Gordon Brown’s weakened position and the low level of the bids attracted raised new question marks over the policy.

The government has been looking to sell a 30 per cent stake to the private sector but has so far not received a bid higher than £2bn. Ministers had previously insisted that they would push ahead with the second reading of the reform bill this month, but this is now likely to be delayed until at least the autumn, according to a report in today's Guardian.

Several ministers, including deputy leader Harriet Harman and the Chief Whip Nick Brown, are known to have argued that the government should abandon the plan altogether. Yesterday the Chief Whip said he was “strongly in favour of a way through this issue that had a buy-in from a majority of the Labour and trade union movement”.

A motion opposing part-privatisation has been signed by 148 Labour MPs and ministers are desperate to avoid another rebellion after Gordon Brown suffered his first Commons defeat over Gurkha settlement rights. They also fear that privatisation could become a rallying cause for those seeking to force Brown out of No 10.

The Business Secretary, Lord Mandelson, who is piloting the postal services bill through Parliament, has previously been determined to ensure that the plan is not diluted but has now conceded that a sale will not take place unless a higher price is offered.

Centre-left figures such as Peter Hain, who returned to government last week as Welsh Secretary, are keen to re-examine a proposal to turn Royal Mail into a not-for-profit company.

The proposal, outlined by the left-wing campaign group Compass, would see Royal Mail become a non-profit company like Network Rail or the BBC Trust.

Ministers previously rejected this option as “unworkable” and a “political fix”. But the plan, which would allow private sector involvement but avoid a divisive sale, is likely to now be reconsidered.