Tory Lord True has been accused of trying to "fool" peers with claims about government plans to demand people show photo ID to vote.
The Conservative minister wrote to members of the House of Lords in a bid to defend Boris Johnson's Elections Bill.
Peers successfully moved to water down the controversial bill in the Lords this week, expanding the number of forms of acceptable ID.
But a move to kill off the voter ID proposals entirely did not succeed.
Ministers have been warned strict ID rules at polling stations will lead to lower turnout in elections and potentially millions of people losing the right to vote.
But in a letter to fellow peers, Lord True defended the move because in Northern Ireland, where photo ID was introduced in 2002, turnout was higher than in other parts of the UK.
He wrote: "...in the first general election after photo identification was introduced (2005), turnout in Northern Ireland was higher than in each of England, Scotland and Wales."
But Lord True did not mention that turnout in Northern Ireland dropped significantly following the introduction of voter ID.
And a Cabinet Office official admitted as much in a letter to campaigners in April 2021, and noted the dip in turnout lasted until 2015, 12 years later.
Writing to Unlock Democracy's Tom Brake, the official wrote: "Across the three main elections in Northern Ireland (General, Assembly, Local), turnout appeared to be lower after the introduction of photographic identification as part of the Electoral Fraud Act in 2002."
"Lord True's claim that the introduction of photo voter ID won't reduce turnout will fool nobody," Mr Brake told the Mirror.
"The Government is already on record confirming that, not only did it reduce turnout in NI, but the effect lasted for 12 years.
"Photo voter ID, with an exorbitant price tag of up to £180 million over ten years, should be scrapped. It serves no real purpose and will make it harder to vote."
Peers voted on Monday to water down the government's plans.
They backed an amendment from Tory ex-minister Lord Willetts to expand the list of accepted identification to include non-photo documents - such as birth certificates, bank statements, council tax demands and library cards.
But the amendment could be stripped out when the bill returns to the House of Commons for its final stage.
Pilots of the voter ID crackdown, which will cost £120m over a decade, showed 740 voters were denied a vote in just 10 areas.
Yet there were just 171 claims of in-person voter fraud from 2014 to 2019 - of which three led to a conviction.
A spokesperson for the Department of Levelling Up, Housing and Communities said: “Everyone eligible to vote will have the opportunity to do so - 98% of electors already have an accepted form of identification, and any that don’t can apply for a free Voter Card from their council.
“We cannot be complacent when it comes to ensuring our democracy remains secure and our Elections Bill will protect the integrity of our elections and stamp out the potential for voter fraud.”
