Nick Clegg will on Wednesday emerge from the disaster of the general election to warn MPs that Britain’s civil liberties hang in the balance, promising to fight measures expected in the Queen’s speech that may compromise Britain’s commitment to the European convention on human rights.

Clegg has said nothing in public since he resigned as Liberal Democrat leader in the wake of his party’s collapse from 57 to eight MPs and the near-loss of his own Sheffield Hallam seat, but the controversy over Conservative plans to repeal the Human Rights Act and introduce a British bill of rights is likely to be one of the most fraught in this opening parliamentary session of the first majority Tory government since 1996.

David Cameron will seek to provide a blue collar tinge to a day of ermine and tradition by pledging that legislation will be brought forward to ensure that future increases to the income tax personal allowance reflect changes to the national minimum wage. The policy foreshadowed in the Conservative manifesto will mean people working 30 hours a week on the minimum wage will not pay any income tax.

No 10 also promised to press ahead with plans, widely ridiculed in the election campaign, for a five-year tax lock – a law which means there can be no rises in income tax, VAT or national insurance in the next five years. Downing Street has billed the Queen’s speech as “a programme for working people from a one-nation government that will bring our country together”.

Parliament will also see battles over planned £12bn welfare cuts. In a report on Tuesday, the Institute for Fiscal Studies thinktank said it was “virtually certain” that some combination of tax credits, housing benefit, disability and incapacity benefits and child benefit would have to be cut to meet the £12bn target.

Other Tory measures likely to arouse controversy include plans on union strike ballots, countering extremism, the in/out referendum on UK membership of the European Union and the right-to-buy scheme for 1.3 million housing association tenants.

Although the government has an overall majority of 12 seats in the Commons, Cameron is massively outnumbered in the House of Lords and his whips will have to be alert to any signs of rebellions by backbench MPs, possibly made restive by the prime minister’s promotion of an insufficiently ambitious EU renegotiation agenda.

Ministers already acknowledge that a conflict over the Human Rights Act may prove to be one of the most difficult politically, legally and intellectually for the Tories, with one wing or the other likely to be disappointed by the measures produced by the justice secretary, Michael Gove.

In a bid to rally his demoralised party, Clegg will tell MPs: “The Liberal Democrats worked hard to ensure that the coalition government’s agenda had a clear thread of liberalism running through it – from the priority we gave to mental health and the green agenda, to creating the pupil premium and protecting our civil liberties.

“So it is dispiriting – if pretty unsurprising – to see how quickly, instead of building on those achievements, the new Conservative government is turning its back on that liberal stance.

“The human rights we hold dear, our right to privacy in an online age, our future as an open-minded, outward-looking country, are all hanging in the balance again because of the measures being announced by the Conservative government.”

He will add: “My party’s parliamentary presence may be reduced in size, but our mission is clearer than ever. As we did in the coalition government, we will fight any attempt to weaken the fundamental rights of our citizens. We will stand up for the poorest and the most vulnerable.

“And we will always defend a Britain that is at its best when it is open-hearted, open-minded and outward-looking.”

Andy Burnham, the shadow health secretary, signalled his determination to make the Human Rights Act a central part of Labour opposition to the Queen’s speech if he was successful in his bid for the party leadership. He said he hoped Labour “throws the kitchen sink” at opposing the measures.

He said: “The Human Rights Act gets a bad press but has ensured that deaths in police custody are properly investigated; that elderly couples are not separated when local authorities put them in different care homes; and gay people are not discriminated against.

“We have seen far too many examples in recent times of the state riding roughshod over the vulnerable, as I know only too well through my work on Hillsborough. Labour must always be there to help vulnerable people stand up against government agencies, public bodies and large corporations and that is why, under my leadership, we will oppose any attempt to replace the act with a new set of rights approved only by this government.”

The shadow lord chancellor, Lord Falconer, has already said the lack of clarity in the Tory manifesto means the Lords would be within their constitutional rights to throw out a Conservative rewrite of the Human Rights Act if this ended with the UK parliament explicitly not being subject to the jurisdiction of the Strasbourg-based European Court of Human Rights.