The latest crisis to hit the nationalist, right-wing government erupted earlier this week when a political colleague of one of Poland's deputy prime ministers, Andrzej Lepper, claimed that she had sex with him in 2001 to get a political job.

Aneta Krawczyk, an employee of the ultra-nationalist SelfDefence party, also said that to keep her post she was required to have sex with another leading figure in the party, Stanislaw Lyzwinski, whom she said fathered her daughter.

Both Lepper and Lyzwinski deny the allegations and have suggested that they were invented to destablise the coalition and bring down the government.

On Friday, Lyzwinski underwent a voluntary paternity test at a medical institute in the city of Lodz, and said that the results are expected tomorrow. Meanwhile, chief prosecutor Janusz Kaczmarek said authorities continued to question witnesses in the case.

Another scandal emerged when a Polish newspaper, Dziennik, published a home video damaging to another coalition party, the ultra-Catholic League of Polish Families. The film purported to show supporters of the party at a rally burning a large swastika and chanting the Nazi salute "sieg heil". An aide to a top party member was dismissed after she was photographed at the rally.

The incidents are just the latest problems to beset the government led by the identical twins Lech and Jaroslaw Kaczyinski, who are president and prime minister respectively.

Renowned for his volatility, Lepper has already left the government once only to be reinstated. During that crisis in September, the prime minister said that Lepper had been given "a chance to participate in a good government", but had "failed to use this opportunity and after a short while he returned to his old practices, to troublemaking".

Lepper hit back, describing the action of Kaczynski and his identical twin brother as "boorishness, boorishness and again boorishness."

Shortly afterwards, Poland suffered a second convulsion when a senior aide to the prime minister was filmed secretly offering financial and political inducements to persuade an MP to switch parties. Prime minister's chef de cabinet, Adam Lipinski, held two meetings with Renata Berger, an MP from Lepper's Self-Defence party in which Ms Berger was asked what post she would want if she were to switch party.