Furious Tory backbenchers lined up to take pot shots at one of their own ministers during a Commons clash over the £9 million taxpayer-funded pro-EU leaflet that has begun landing on voters' doormats.
Former Commons deputy speaker Nigel Evans said the Government was using the "spiv" tactics of Zimbabwe's Robert Mugabe while ex-cabinet minister John Redwood branded the move an "insult" to voters.
More than 200,000 people have signed a petition demanding that the Government abandons the plan but the pamphlet began arriving at homes in England on Monday - with delivery to Scotland, Wales and Northern Ireland delayed until after elections to devolved governments in May.
Europe minister David Lidington faced persistent heckling, including cries of "shame", from MPs sitting on the benches behind him as he defended the decision to send out the booklet at a cost equivalent to 34p per household.
He told MPs there is "clear evidence" from independent polling research that voters want more information.
"I am spending time virtually every day now signing replies to Members of Parliament who have enclosed letters from constituents where those constituents have said they feel they do not yet have enough information on which to take an informed decision and they would like to have some more please," he added.
Mr Evans (Ribble Valley) said: "As a member of the Council of Europe, part of my responsibility is election observing and I go round and I have a look at the conduct of the campaign prior to polling day.
"If I witnessed in any of the countries that I go to the sort of spiv Robert Mugabe antics that I've seen by this Government then I would condemn the conduct of that election as being not fair."
A Eurosceptic threat to derail Chancellor George Osborne's Budget in protest failed after the amendment to the Finance Bill, tabled by Sir Bill Cash, was not selected.
David Cameron earlier warned the UK's security would be at risk if the country voted to leave the EU and accused Brexit campaigners of "gambling with our country's fortunes".
Writing in the i newspaper, the Prime Minister said: "The world is increasingly divided, so it's vital we choose unity. Western values are under threat - we must stand with those who share them."