Ipsa officials have remained defiant since the possibility of a siginificant hike in pay emerged this year and the organisation's chief executive, Andrew McDonald, has insisted the public have a "more sophisticated" view of the proposed package than they are being given credit for.
"This is an issue where the public has a more nuanced, and split, opinion than the reactive howls of 'outrage' from some commentators and politicians," he wrote on Ipsa's website.
"The package we will announce on Thursday will, taken as a whole, not cost the taxpayer a penny more," he added.
"That message has not been heard in the hubbub of the last few days."
Ipsa is planning a squeeze on MPs' pensions in a bid to cancel out the £4.6 million cost to the public purse. A £2.5 million saving by downgrading the final salary scheme to career average - matching the rest of the public sector - had already been proposed alongside a crackdown on various perks.
The watchdog responsible for MPs' pay is expected to confirm plans to introduce an 11% pay rise amid threats that the controversial proposals could lead to the organisation being axed.
Ed Miliband has called on David Cameron and Nick Clegg to accompany him to a meeting with the Independent Parliamentary Standards Authority (Ipsa) to demand it halts the wage hike.
In a letter, the Labour leader says the pay increase "undermines confidence and trust in our political system".
Yesterday the Prime Minister issued a veiled threat to abolish Ipsa if it presses ahead with the planned rise after the 2015 general election, insisting it was "simply unacceptable" that Members' salaries would increase increasing by £7,600 to £74,000.