Keir Starmer warns unions of difficult decisions on salaries

Sir Keir also called for a “policy of partnership” between government, business and workers.

He stressed: “Company leaders are not knocking on my door and telling me they want to curtail workers’ rights.”

He said that, like the unions, they wanted “fair taxes, high qualifications and the ability to make long-term investments”.

In the run-up to the election, Labour sought to win over business leaders to support the party and now claims to be the party of both business and workers.

She has promised a reform package to strengthen workers’ rights, externalincluding the right to protection against dismissal, parental leave and sick pay from day one for all employees, as well as the ban on ‘exploitative’ zero-hour contracts.

Trade union leaders have warmly welcomed Labour's election victory and praised the party's plans on workers' rights.

However, some fear that pressure from business associations could lead to a further weakening of the measures after some promises were already watered down before the election.

The Institute of Directors said business leaders were concerned about the impact of the proposals on staff costs, which would make companies less willing to take on new staff.

Conservative shadow business minister Kevin Hollinrake claimed there was “vocal opposition from business leaders” to the government's plans.

“[The prime minister] is simply doing what his backers, the unions, are demanding: raising taxes and drowning companies in a flood of new regulations and bureaucracy along the lines of the French model,” he said.

The Prime Minister's promise to repeal Conservative-era laws that raised the strike threshold and deliver “the biggest convergence of workers' rights in a generation” sparked jubilation among union members.

However, during his speech he was also confronted with the slogan “taxing the rich”.

On Monday, congressional delegates voted overwhelmingly in favor of a wealth tax on the richest one percent of the population to fund public services and the British health care system.

Trade union leaders also criticized the decision to cut heating cost subsidies for millions of pensioners in winter.