The BBC has been forced to apologise after television presenter Jeremy Clarkson said British public sector workers taking part in a 24-hour walkout should be shot in front of their families.

The national broadcaster issued an on-air apology, saying Clarkson's comments in an interview on the BBC One live talk show, The One Show, were a misjudged attempt at comedy.

When asked what he thought of the strikers, Clarkson said: "I would have them all shot".

"I would take them outside and execute them in front of their families," added the presenter, best known as the face of the BBC's top-rated Top Gear car show.

"I mean how dare they go on strike when they have these gilt-edged pensions that are going to be guaranteed, while the rest of us have to work for a living?" he said.

Unions said up to 2 million teachers, nurses and border guards protesting over pension reform staged Britain's first mass strike for more than 30 years on Wednesday, in a confrontation with the government over its austerity measures.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 2 minutes 2 m Millions strike in UK over pension changes

Workers are angry they are being asked to contribute more to their retirement and work for longer before they are eligible for pensions.

Around half of the UK's state schools were closed and thousands of operations were cancelled in hospitals around the country.

Prime minister David Cameron played down the impact of the strike, calling it "something of a damp squib", saying 40 per cent of schools were open and the main London airports were working smooth.

Outspoken Clarkson previously caused outrage when he described former prime minister Gordon Brown, who lost his sight in one eye in an accident suffered while playing rugby as a teenager, as a "one-eyed Scottish idiot".

AFP/ABC