Tory big beast Iain Duncan Smith has branded Ed Balls' cash-in-hand advice "absurd" after the shadow chancellor urged people to keep every receipt of a job.
The work and pensions secretary said Labour had a "complete lack of understanding" about how business works and "how people get by".
"Here we have a man that would be the Chancellor who is wandering around saying Big Brother is going to watch you carefully that if you do any tax transactions and don't keep receipts, somehow they're going to punish you. I find that absurd," Duncan Smith told BBC Breakfast.
The criticism comes after Balls attempted to put further pressure on the Conservatives following the HSBC tax avoidance scandal.
The shadow chancellor said the "right thing to do" was to ensure that any jobs paid with cash were recorded properly.
Asked on the BBC's Andrew Marr show if he followed his own advice, he added: "Absolutely. That's because I am the shadow chancellor and I'm extremely careful about these things.
"Over my life, have I ever given people a tenner and not been given a receipt for it? Probably yes."
Balls' shadow cabinet colleague, Chuka Umunna, took to the airwaves this morning to defend the shadow chancellor.
"The whole way we do politics and debate things in this bubble, it's just so ridiculous because he was doomed if he did and doomed if he didn't in answering that question and it's all over the papers this morning. And actually, it's a bit of a storm in a teacup," Umunna told Sky News.
Ed Miliband plans to sure up his business credentials later today (16 Feburary) and call for "more inclusive prosperity".
The Labour leader, in a speech at Jaguar Land Rover in Wolverhampton, is expected to unveil his "modern industrial strategy" for Britain.
"We need a plan which nurtures the talents of every young person, supports every business, allows every family to share prosperity, and expects each and every one of us to contribute," he will say.
The speech will come with 80 days to go before the general election, with Labour on a three point lead over the Tories (35% vs 32%), with Ukip on 15%, the Liberal Democrats on 7% and the Greens on 6%.