Theresa May has been warned not to abandon Margaret Thatcher’s free market economics as she prepares to reveal the most interventionist Tory manifesto for generations.

Cabinet ministers and advisers who served under Mrs Thatcher have told The Sunday Telegraph of their fears about Mrs May’s economic direction.

The Prime Minister has already announced an energy price cap and is expected to clamp down on executive pay and empower workers on boards in her election pitch.

Her more interventionist economics, which is part of an election strategy to win over traditional Labour voters, has triggered a backlash among some Tory grandees.

Lord Tebbit, who held the trade and employment briefs under Mrs Thatcher, said Mrs May “would be wise” to “extend” the Iron Lady’s free-market thinking.

“We should not be drawn to the Left in order to occupy the mythical central ground between us and our principal opponent”, he warned.