Two students from the University of Chester have apologised after they entered a Halloween fancy dress competition in costumes depicting the 9/11 terrorist attack on New York's Twin Towers.

Amber Langford and Annie Collinge, both 19, were even awarded first prize at Rosies nightclub in Chester, winning £150 in shopping vouchers.

Yet they have been criticised today by relatives of those who died when two planes crashed into the World Trade Centre on 11 September 2001, after their picture was published on the front page of The Sun under the headline: “Towering stupidity”.

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The girls’ costumes, which were labelled North Tower and South Tower, featured planes hanging from the buildings amid explosions. They wore hats that were meant to look like smoke billowing out, apparently also showing people jumping to their deaths from upper floors, and all of it topped with miniature American flags.

Ms Langford’s father, who according to The Sun’s report was flying a United Express jet in the US at the time of the attack, said he would be “having a little chat” with his daughter about the incident.

“I didn't know anything about it, but I'm not happy at all,” Martin Langford said. “She knows I'm a pilot and that's not cool.”

The students told the newspaper: “We never meant to be offensive, but we apologise if any offence was caused.

“The idea was to depict a serious, modern-day horror that happened in our lifetime and was not intended as a joke.”

A spokeswoman for the Stonegate Pub Company, which runs the nightclub, said: “Following the club night Halloween promotion that took place at Rosies, Chester, we are extremely concerned that an award of shopping vouchers was made to two young women who were dressed in a distasteful and offensive manner.

“There was a serious error of judgment made on the evening by a contracted DJ to award such a prize and we apologise to anybody who may have been upset or offended by this. A full investigation by the company is taking place.”

The University of Chester and Chester Students' Union said in a joint statement: “We utterly condemn the appalling photos. Both organisations have begun an urgent investigation with a view to taking the necessary action.”

Patricia Bingley, 79, whose son Kevin Dennis was among the 67 British people killed in the 9/11 attack, said: “This is unbelievable – 9/11 happened in their lifetime.

“It’s hard to understand where they’ve come from to do this without a thought for those who died or the families left behind.”