Media playback is unsupported on your device Media caption Ed Balls: "His surname has just gone from my head, which is a bit annoying"

Shadow Chancellor Ed Balls has said "it's an age thing" after failing to remember the name of one of Labour's main business supporters.

In an interview with BBC Newsnight, he described Bill Thomas - who helped draw up the party's small business policies - as simply "Bill" and when pressed could not give his surname.

Labour sources called it "a human error" and a "perfectly human slip up".

Mr Balls tweeted on Tuesday: "It's an age thing!"

David Cameron seized on the gaffe at Prime Minister's Questions, saying it was evidence that Labour was "anti-business and anti-enterprise".

"The shadow chancellor was asked whether he could think of one business leader (who supported Labour) and do you know what he said?

Media playback is unsupported on your device Media caption David Cameron: "Bill somebody is Labour's policy"

"He said 'Bill somebody'. Bill somebody is not a person. Bill somebody is Labour's policy," he said - a joke greeted by cries of Bill from the Conservative benches.

Labour leader Ed Miliband hit back, saying the Conservative Party was the party "of Mayfair hedge funds and Monaco tax avoiders".

He suggested that David Cameron was unwilling to clamp down on City firms not paying stamp duty on share deals because many of his friends "would get caught in the net".

"Under him, there is one rule for those at the top and one rule for everyone else."

In the Newsnight interview, Mr Balls was being quizzed about whether Labour was anti-business, following criticism by Boots boss Stefano Pessina.

Analysis by political editor Nick Robinson

The Labour leader knew that if he dared to raise anything about the economy at Prime Minister's questions he'd face taunts about Ed Balls's struggle last night to name a single prominent business backer of the party. So why did he take the risk?

Read Nick Robinson's blog

The shadow chancellor said he had just been at a dinner with some of Labour's business supporters including "Bill, the former chief executive of EDS, whom I was talking to just a few moments ago ... he is a big supporter of ours."

When presenter Emily Maitlis asked what Bill's surname was, he said: "It has just gone from my head, which is a bit annoying at this time of night…"

The Shadow Chancellor later tweeted an explanation for his memory lapse: "I know, I know. Bill Thomas, our Small Business Taskforce Chair, will never forgive me. It's an age thing!"

Speaking later to the BBC, Mr Thomas said: "I absolutely back Labour and I absolutely believe in Ed Miliband.

"I've spent a significant amount of time with Ed Miliband going through the contents of my report talking through various policy areas and I believe that Ed Miliband has a compelling vision for what kind of country he wants to lead as prime minister."

Who is Bill Thomas?

William Gennydd Thomas is an IT expert and former senior vice president of Hewlett Packard Europe. He also sat on the board of HP subsidiary Electronic Data Systems, a business services company founded by one-time US presidential candidate Ross Perot.

The father-of-three rose from humble origins in Lancashire to head the multinational business, which employs about 50,000 people. He reportedly took early retirement at the age of 50, to concentrate on running his historic country mansion Hopton Hall, set in 30 acres of land in Derbyshire, where he lives with his wife Julie.

In 2013, he was drafted in by Ed Miliband to chair Labour's "small business taskforce", which was given the job of coming up with policy ideas for the party's general election manifesto. Mr Miliband hailed the "enormous commitment and imagination" Mr Thomas had brought to the job, when the report was published.

Mr Thomas is on the board of the Co-operative Bank, is chairman of the advisory board of Cranfield University School of Management and is on the management and Board of Leeds University Business School. He is also a non-executive director of tech firms XChanging plc and GFI SA, and of construction giant Balfour Beatty.

Lord Jones, the former CBI chief, who also served as a trade minister in Gordon Brown's government, said Mr Balls's slip was indicative of "a much bigger problem with business" for the Labour party.

"They haven't got the support that New Labour used to have years ago," he told BBC Radio 4's Today programme.

The founder of upmarket fast food restaurant chain Yo Sushi! also joined in the criticism.

Simon Woodroffe, a former Labour supporter who has since donated money to the Conservatives, said he believes Ed Miliband is promoting a populist anti-business message: "He's saying 'look at these fat cats making lots of money, it should be for the workers'.

"What I want our leader to say is 'We want enormous profits, and yes we are going to share them out later, but first of all we've got to make them'," he told Newsnight.

'Pro-business party'

But Labour's biggest individual donor, home shopping magnate John Mills, said claims that the party was not on the side of business, had been "blown up beyond all reasonable bounds".

Image caption Former restaurant chain boss Simon Woodroffe joined in with the criticism of Labour

"Some of the comments that have been made over the past few days have been really rather poorly judged because these companies are going to have to work with a Labour government if it gets elected in 2015," he told BBC Radio 5 Live.

He added: "No government can work successfully if it doesn't have the business community's interests at heart, and I'm sure Labour will do so when it gets elected."

Mr Balls insisted Labour is "the pro-business party today" following the row with Mr Pessina, who said he feared a 'catastrophe' for business if Labour wins May's general election.