Iain Duncan Smith has failed to rule out future cuts to the benefits of well-off pensioners.

The Conservative Welfare Secretary played down suggestions he would need to reduce payments such as the state pension to help cut the welfare bill. But he dodged the issue of universal benefits – which include the Winter Fuel Allowance, worth hundreds of pounds a year.

The Tory-LibDem Coalition has faced heavy criticism from opposition parties and churches over its welfare reforms.

The SNP said yesterday was Westminster's "day of shame" while Labour has dubbed this month "black April" following the introduction of a series of measures – including the so-called "bedroom tax", a cut in the housing allowance for council tenants with a spare room.

There have also been warnings the public should brace for more cuts as the Coalition keeps to its austerity agenda.

The respected Institute for Fiscal Studies (IFS) think-tank predicts the UK faces higher taxes or deeper cuts after the next General Election to deal with the country's economic difficulties.

Critics say universal benefits are wrong as they help those who least require them. But advocates warn many of the payments would cost more to means test.

In an interview, Mr Duncan Smith defended the Coalition's welfare reforms, saying they were necessary to free people from a life trapped on benefits.

Asked if future savings would be made by cutting benefits to older people, including universal benefits, he said steps were being taken to protect vulnerable pensioners.

"Those of working age we believe, working with them, we can help them change their prospects through work and through better support," he said. "But those who are pensioners, of course they're the most vulnerable because they can't. So we have absolutely ensured that pensions rise above inflation and certainly above income by 2.5% extra.

"I'm pleased about that – that is the right thing to do, but controlling welfare is critical," he added.

Mr Duncan Smith also said that thanks to the Coalition's reforms "people will be saving more [towards their pensions] as they go forward".

He denied claims he was "slashing" welfare , insisting the Coalition was improving the system to make it fairer.

Steve Webb, the Liberal Democrat pensions minister, also defended the bedroom tax reforms – saying they would cost families an average of £2 a day to have a spare room.

The Scottish Government has criticised the bedroom tax, which it warns will impoverish Scottish families.

SNP MSP Jamie Hepburn, deputy convener of the Scottish Parliament's Welfare Reform Committee, said the welfare reforms were "catastrophic" and "hurting the life chances of people who depend on the support of the welfare state".

Tory chairman Grant Shapps attracted derision over the weekend when he said his children had to share a room. It later emerged the MP uses a spare room in his four-bedroom house as a study.

Citizens Advice Scotland (CAS) warned there was a "severe mis-match" between the need and the supply of one-bedroom homes, one of the reasons that ministers have cited for the bedroom tax.

CAS warned: "Many will find that they have little choice but to try to cope with reduced support on a low income. In this situation, it is inevitable that some will fall into arrears and face potential homelessness."