Mr Persson (right) and Mrs Freivalds claim the adverts were offensive

Mr Persson and former minister Laila Freivalds - who was also pictured - said the ads were offensive and their images were used without permission.

The ads were published last year at a time when the government was under fire for its response to the Asian tsunami.

Ryanair said it would vigorously defend itself in court.

'Hurtful ads'

It described the legal action as a "complete waste of taxpayers' money".

Mr Persson and Mrs Freivalds are seeking damages of �5,614 ($9,827; 8,060 euros) each from the Irish airline for unauthorised use of their pictures.

Promoting cheap flights to Germany, Poland and Latvia, the ads were published in the build-up to parliamentary hearings into Sweden's response to the Asian tsunami.

We will defend the right of free speech and also the right of consumers to have low fare air travel Lotta Lindquist, Ryanair

The government was criticised for its actions after the disaster, in which about 550 Swedes died.

Mrs Freivalds resigned from the government earlier this year.

Lawyers for Mr Persson said the timing of the ads was offensive.

"The use (of the pictures) has caused suffering and is apparently hurtful," solicitor Lennart Kanter said.

The duo launched proceedings after Ryanair did not pay an invoice for use of the pictures, Mr Kanter added.

'Stifling competition'

In response, Ryanair said the government was seeking to stifle competition in the aviation market.

It cited proposals to introduce an environmental tax on commercial air travel as evidence of the government's efforts to "deny Swedish citizens access to low cost travel".

"We will defend the right of free speech and also the right of consumers to have low fare air travel," said Lotta Lindquist, the airline's Scandinavian sales manager.

Ryanair has often courted controversy with its advertising.

Last year, it was criticised for running a series of adverts after the London terrorist bombings headlined "London Fights Back".