LONDON (AFP) - Hundreds of thousands of British nurses, midwives and hospital cleaners went on a four-hour strike Monday calling for a pay rise, weeks after walking out for the first time in 32 years.

Eleven health worker trade unions took part, calling on the government to approve a one-percent wage rise for National Health Service (NHS) employees recommended by an independent pay review body.

Picket lines were set up outside hospitals, although emergency departments were kept open.

"The anger is spreading and so is the public support for the health workers' cause," Dave Prentis, leader of the Unison union, said at a picket outside the London Ambulance Service headquarters.

Unions say that by 2015, health workers will have had their pay capped for six years.

The strike comes ahead of the May 2015 general election, and both parties are putting the state-run NHS at the heart of their campaigns.

The opposition Labour Party accuses the Conservatives of planning to dismantle the health service by privatising parts of it, and has promised more funding.

Conservative Prime Minister David Cameron has accused Labour of scaremongering and has vowed to protect the NHS budget from spending cuts.