David Cameron has called for a "rapid review" on the constitution of the House of Lords after they voted against the government for the first time in 100 years.
The Prime Minister's plans to cut tax credits have now been delayed after two motions were passed by peers.
A Number 10 spokesman said: "The Prime Minister is determined we will address this constitutional issue.
"A convention exists and it has been broken. He has asked for a rapid review to see how it can be put back in place."
They are not there to interfere with the settled will of the House of Commons, warned Boris Johnson.
A working mum who would be hit by Tax Credit cuts spoke to ITV News ahead of the House of Lords vote on the changes.
Peers will have to decide whether to delay changes to the tax credits bill, review them or scrap it altogether.