The war of words between MPs and the new expenses regulator escalated today, with the watchdog branded a "nightmare" and accused of being responsible for major security lapses.
The Independent Parliamentary Standards Authority (Ipsa) has moved to calm anger among MPs, promising more face-to-face meetings.
But in Parliament today, MPs complained the organisation was too bureaucratic and had resulted in serious breaches of privacy.
Labour's David Winnick (Walsall N), who was one of the leading campaigners for greater transparency in the expenses system, said it was "very difficult indeed to get any sense out of Ipsa".
Opening an unusually well-attended debate in Westminster Hall, he said: "It is indefensible that Ipsa should have set up a system which is so difficult and so complex, and, particularly for new members, has made life a nightmare."
Mr Winnick, who repeatedly hammered on the table in anger as he made his speech also hit out at the number of spin doctors being recruited by Ipsa, including a communications director earning up to £85,000.
"You do ask yourself why on earth Ipsa should require three spin doctors, why any spin doctors?"
Phil Wilson (Lab, Sedgefield) was given an ironic round of applause by MPs as he said he had succeeded in logging on to the online expenses system.
But, he added: "The expenses that appeared on the screen were those of another MP."
Ipsa told him it was a "glitch" but Mr Wilson said: "In my view that is not a computer glitch, that is a gross intrusion into another member's privacy."
Veteran Labour MP Dennis Skinner (Bolsover) said he had a message sent to him this month by Ipsa which belonged to another MP and claimed other politicians had received emails intended for other recipients.
He warned: "This system will end in tears if we are not careful.
"It's not about Ipsa, it's not about being an independent body - we all welcome that, we all voted for that, it's about the fact that it is not secure.
"In a few weeks we have already seen established many, many examples of insecurity ... they must look for a different system in order to get the show on the road."
Anger has focused on the new system requiring MPs to foot the bill for constituency office costs and then claim the money back, instead of payments being made directly by the authority as happened previously.
MPs have also argued that a cap on the amount they can pay in office rent will force some into unsuitable premises and that a reduction in staffing allowance could lead to employees being laid off.
Tory Sir John Stanley (Tonbridge and Malling) called for the Standards and Privileges Committee to investigate whether Ipsa was obstructing the work of MPs.
He said: "Nobody can say with certainty at the moment whether Ipsa is violating the privilege of freedom from obstruction, because that is a matter for the House and only for this House of Commons.
"But equally nobody can reasonably deny that this is an issue that must be addressed by the House and as early as possible in the life of this Parliament."
Tory Richard Bacon (S Norfolk), a member of the Public Accounts Committee in the last parliament, said the National Audit Office could investigate whether Ipsa was providing value for money.
Shadow justice secretary Jack Straw, who steered the legislation setting up Ipsa through the Commons, was heckled by MPs as he attempted to justify the body.
He said Ipsa had "failed to take account of the reality" of the way MPs work and the need to set up their own offices.
Turning to the much-criticised online system, he said: "It's not the IT system that is going to stop ... abuse of the system, it's the total transparency of it, that alone."
Cabinet Office minister Mark Harper said Ipsa would review the scheme in the autumn and examine the possibility of a direct payment system.
Many MPs called for a simple credit card system and Mr Harper said he "was sure they will have listened to the advice" on that.
"They very much recognise that looking at a direct payment system for office costs is a very sensible venture," he said.
Ipsa today announced a series of measures aimed at placating MPs' fury, including an extension of the deadline for repaying advances of up to £4,000 for up-front costs and additional help in using the online expenses system.
The regulator's chairman Sir Ian Kennedy told The Times today that some MPs had apologised for their treatment of Ipsa staff and said he had been "surprised" at the hostility "bordering on rudeness" they had faced.
In a statement announcing the new steps Ipsa was taking, Sir Ian acknowledged the early days of the new system had been "challenging".
He said: "It is six weeks since the new rules on MPs' expenses were introduced. In that time Ipsa has laid induction and training for almost 600 MPs, paid all MPs' salaries on time and is on track to pay the first batch of expenses on June 23 as planned.
"Yet, as we have always said, this implementation period is an extremely challenging one for MPs - and for Ipsa.
"The new rules represent a complete break from the past. Independent regulation requires a significant cultural and organisational change of approach from what went before.
"Where we can assist MPs to adapt to these changes and ensure the pressures on our staff are eased we will do so, and the measures we are announcing today to improve the advice we offer should help do that. But the new rules are fair, workable and transparent, and are here to stay.
"Restoring public confidence in the expenses system will take time. The new rules, and the system of openness and scrutiny that go with them, will play a major part in achieving this goal.
"But MPs must show demonstrate their responsibility to making the new system work too."
The body published consultations today on the role of new compliance officer Alan Lockwood, including his investigatory powers and the penalties he can impose on errant MPs.
A consultation is also being launched on the future publication of MPs' claims - including the level of detail of information on items such as the addresses of taxpayer-subsidised homes.
Prime Minister David Cameron's spokesman said it was "unacceptable" for MPs to abuse Ipsa staff, but acknowledged there were "issues" with the expenses regime.
He said: "There is a new system being put in place. Clearly that system has to be made to work properly.
"As with any new system there are some issues with getting it working."
Asked if was acceptable for MPs to abuse Ipsa staff: "I think abuse of members of staff is something we all find unacceptable."Reuse content