The wife of Lord Kinnock’s son has had to deny that her husband is gay as she battles to become Denmark’s new prime minister.

Helle Thorning-Schmidt, the leader of the Social Democrats, said her family had been hit by a “grotesque” smear.

Rumours say she and Stephen Kinnock have split after 15 years of marriage and one newspaper claimed today that Mr Kinnock was gay.

Ms Thorning-Schmidt, 44, told Denmark’s Ekstra Bladet: “I can only say it is not true.

“It is very unpleasant that newspapers print such rumours and I am also sorry that generally there are these rumours about politicians. It’s really uncomfortable, also for my family and my children. It’s so grotesque.”

Mr Kinnock lives and works in Geneva. Yesterday, he flew to Denmark to be seen alongside his wife.

Ms Thorning-Schmidt holds a narrow lead in the polls but there has been talk of a “Kinnock curse”.

In 1992, her father-in-law, the Labour prime minister candidate, appeared set for victory but lost out to John Major’s Conservative Party.

Ms Thorning-Schmidt has also faced criticism for her luxury lifestyle, while the couple have been accused of trying to avoid paying taxes.