The unofficial opposition shows its teeth

Outspoken backbenchers line up to attack the PM over privatisation and his kowtowing to George Bush

Tony Blair's relationship with his own MPs is heading for turbulent times, backbenchers have warned.

As the House of Commons broke up for the long summer recess, Labour MPs – disillusioned by the direction of the leadership or disgruntled at missing rewards for loyalty in the post-election reshuffle – threatened that the outspoken, rebellious atmosphere at Parliament in the past few weeks could continue.

Many are furious about Mr Blair's as-yet unexplained commitment to increasing the role of the private sector in funding hospitals, schools and public transport. Other possible flashpoints are welfare reforms, including plans to "MoT" people claiming disability benefits, and changes to people's working rights felt to be too favourable to business. Labour MPs are also hostile to the controversial US-led plans for a national missile defence system. Last week Labour MPs were infuriated by hints at a meeting with the Foreign Secretary, Jack Straw, that Britain would ultimately back the "Son of Star Wars" programme championed by George Bush, the US President.

"He has massively misjudged the mood on the Labour backbenches," a senior Labour MP said. "I think the problem lies with Blair. He is so temperamentally attached to the centre ground he can only be moved to the left by a concerted and vigorous and sustained campaign. He will never do it of his own volition.

"The Prime Minister has never taken a close interest in the PLP [Parliamentary Labour Party] and its members. Now the PLP just feels distanced from what the Government is proposing."

MPs have put their faith in the Parliamentary Committee, a group of Labour backbenchers which meets the PM every week to discuss concerns. Some of its members, including Ann Clwyd, Gordon Prentice and Andrew Mackinlay, have been among the more outspoken critics of certain aspects of New Labour's policy and practice.

Labour backbenchers are also keen to have a debate about their links with the Government, which could be based on a document prepared by the former chairman of the PLP, Clive Soley.

"People are finding their feet, flexing their muscles and people are obviously here in their second term and are a bit stung by criticism that they are weak," a long-serving Labour MP said. "You can expect more vigour from those people, certainly. They will be more prepared to speak up now when ministers signal changes they don't approve of."

Another added: "Core values are things that people will want to see achieved in the next session."

The first signs of internal opposition to the Blair regime came immediately after the election.

The trade unions are still unhappy about the Government's proposals for the future of public services. They plan a showdown with the leadership during the autumn conferences over increased use of private firms. Union bosses are already threatening to withdraw funding from the Labour Party and fight campaigns with other political groups, including the Liberal Democrat Party.