Outgoing employment minister Chris Grayling has been heckled in a parliamentary debate as he defended Government use of Atos Healthcare to carry out fitness to work assessments.

Mr Grayling, the new Justice Secretary following the Government reshuffle, faced shouts from the public gallery in Westminster Hall, an annex to the main Commons chamber.

Chairman of the session Philip Hollobone threatened to suspend the sitting after protesters in wheelchairs shouted "shame on you" and "people's lives are at stake". Interruptions were made twice and one woman was escorted from the room.

Mr Grayling did not respond directly to the claims but did defend the Government's policy to assess whether people were capable of work. He said: "This is not an exact science. We will never create a system which is perfect."

The 90-minute debate was called by Labour's Tom Greatrex, MP for Rutherglen and Hamilton West.

Atos has faced protests over its assessments, particularly since the company's brand was displayed prominently on London 2012 lanyards, as the firm is a sponsor of the Paralympic Games.

Responding to the debate, Mr Grayling said the decision to carry out work capability assessments was a "long and difficult process" but insisted there were no targets on savings or the number of people to take off benefits. He told the MPs: "I believe if people can return to work, even if it is a different form of work to the work they did before they had health issues arose, (they should)."

Mr Grayling was interrupted at this stage of his speech. Mr Hollobone said: "Parliamentary rules are there are to be no noise at all from the gallery. If you persist, madam, I will have no choice but to suspend the sitting and clear the gallery. This is your last chance. If there is more noise, I will have to suspend the sitting, no one will hear from the minister and I will clear the gallery."

Mr Grayling continued: "It is about finding the right number of people who can make a return to work. It is not an exact science, it never was and never could be. But it is all about trying to help people back into the workplace if they possibly can be. That was the motivation of the previous government when it established the work capability assessment."

Mr Grayling said Atos Healthcare was not responsible for making any decisions about benefits. He said the Atos staff carry out assessments designed by Government, and "decision makers" in the Department for Work and Pensions reach a verdict. He added: "We will never create a system that is perfect. That is why we have a right to appeal."