William Hague has come under fire after he mouthed the words "stupid woman" at a Labour MP during prime minister's questions.

The foreign secretary's remarks on Wednesday came after his links with Conservative donors and private companies were called into question by shadow treasury minister Cathy Jamieson. Hague later said that he did not intend any offence.

Jamieson asked David Cameron: "Perhaps the prime minister could tell the House whether [Tullow Oil chief executive] Mr Aidan Heavey's donations to the Conservative party had any influence on the foreign secretary's intervention in his company's tax dispute?"

As the prime minister responded, Hague was seen to mouth "stupid woman" twice.

Jamieson later told the Huffington Post: "I didn't hear what Mr Hague was saying but immediately after PMQs I was contacted by constituents and others who were outraged that he was apparently muttering before I had even finished my question. It would have been better for the prime minister to give the House the reassurance I sought than have the foreign secretary muttering insults from the sidelines."

Fellow Labour MP Michael McCann tweeted that Hague's words were "scandalous" while Labour MEP David Martin demanded that the foreign secretary apologise.

Speaking in the Commons later, Hague said: "I mutter many things in this House. Others shout them rather louder than I do, but I mutter many things under my breath and never intend any offence to any other honourable member."

Nevertheless, his insults are likely to raise fresh concerns about sexism on the Conservative frontbench at time when the party is struggling to attract female voters. An ICM/Guardian poll in February put Labour ahead of the Tories by 26 points (51% to 25%) among women, compared with seven points (36% to 29%) among men.

Cameron has also been accused of insulting female MPs in the past. In 2011, he told the Labour MP Angela Eagle to "calm down, dear" and referred to his own MP Nadine Dorries as "frustrated". Minutes before Hague's remarks to Jamieson, the prime minister was jeered by Labour MPs as he described Andy Murray as "the first British player to win Wimbledon for 77 years", rather than recognising that he was the first British man to do so.

Labour leader Ed Miliband corrected him, saying: "Let me first join you in paying tribute to Andy Murray for his fantastic victory following Virginia Wade's victory in 1977." A Downing Street source said the prime minister's mistake was "not the worst crime in the world".