The current House of Lords risks becoming bloated and dysfunctional while reform proposals are debated, MPs have warned.
A report from the Commons' political and constitutional reform committee has called on the prime minister to cease making new appointments to parliament's upper House to address the problem.
Its calls, which mirror those of a recent report from the UCL's Constitution Unit, follow an unusually large intake of peers after the general election which insiders say has left the Lords creaking under the strain.
Mr Cameron ennobled 61 new peers after May 2010, while outgoing prime minister Gordon Brown made 56 as he left Downing Street.
"This has led to several problems, on which a leader's group in the Lords has reported: risk to the House's reputation, difficulty of conducting business effectively, and pressure on the services provided by the House administration," the report noted.
Although the coalition has pledged to fundamentally reform the Lords by 2015, introducing a wholly or most elected second chamber, MPs say the current problem "cannot wait four years to be resolved".
"The current, effectively untrammelled, process for making party-political appointments to the House of Lords, coupled with the lack of any mechanism for members to leave the upper House, threatens that House's effective functioning in the shorter term," the report adds.
Its findings followed a seminar in which members of the Lords and prominent experts gathered to discuss the problem earlier this year.
"These are the views of experts from all parties and none," committee chair Graham Allen said.
"Whether or not we get radical Lords reform, there are changes here that need to be made now, if parliament is to function effectively over the next few years."