Nick Clegg faces a renewed battle at his party conference with senior MPs and activists who plan to force the Liberal Democrat leader to back a repeal of the government's NHS reforms.

The rebels will pressure the party to outflank Labour on the NHS and further condemn the role of market forces and competition in the health service. They are being supported by senior figures in the sector, including Dr Clare Gerada, former chair of the Royal College of GPs.

The row threatens to overshadow Clegg's final conference before the general election and could distract from his attempts at claiming credit for Britain's economic recovery. The health and social care bill proposed by health secretary Andrew Lansley in 2010 caused divisions within the Lib Dems during the first years of the coalition. The then party whip, Norman Lamb, who is now a health minister, expressed his reservations at the time, although Clegg was able to restore his authority by forcing through changes to the original bill. However, the rebels are determined to reignite the debate and push the leadership at their Glasgow autumn conference into amending the 2015 election manifesto.

The development comes as Clive Stone, a campaigner for an end to the rationing of cancer treatments, who David Cameron said had inspired him to pledge a special cancer fund, warned in a column for his local newspaper that "sadly, we are now closer to privatisation" following the coalition's reforms.

Labour has pledged to repeal the legislation, designed to encourage the outsourcing of NHS services to private firms. The Lib Dem rebels want Clegg to go further and support dismantling the NHS's internal market through which different parts of the system commission and provide services. NHS administration costs prior to the introduction of the internal market were 5%. After 1981 and the introduction of the internal market, they soared. In 1997 they stood at about 12% and by 2010 costs had risen to 14%.

According to a minority report compiled by party members on the Liberal Democrats' public services working group, between 2000 and 2010 the number of NHS managers increased twice as fast as the number of doctors and five times the number of nurses.

John Pugh, a former Lib Dem health spokesman, said: "There is no compelling reason why the NHS in England should be encumbered with this level of bean counting … the NHS should be like other more efficient public services run on simple best-value principles. If the NHS was a patient, then after decades of pointless market-based treatment it would surely be seeking a second opinion."

Dr Charles West, who led the conference opposition to Lansley's controversial 2012 Health and Social Care Act, which resulted in its delay and revision, told the Observer: "There are no doubt some in the party who want to let the dust settle, but frankly the Lansley bill solved no problems and created some new ones.

"The problems of acute financial pressure and poor integration of services aren't going away. The NHS internal market is one of the few in the world that actually costs us all.

"For too long the NHS has been tinkered with by politicians pursuing ideological and unproven theories. Here, for a change, is a policy based on the evidence and supported by clinicians.

"It will make it easier to provide a high-quality integrated service to all patients wherever they are and will save billions of pounds compared to the market-driven service we have at the moment."