A worldwide ban on the use of cluster bombs is being called for by the international development secretary.
Cluster bombs were used in Iraq
Hilary Benn said they had a very serious humanitarian impact and likened them to land mines, which were banned under international law in 1999.
The comments by Mr Benn, who is hoping to succeed Labour deputy leader John Prescott, were in a letter to cabinet colleagues leaked to the Sunday Times.
A charity says 10,000 people have been killed or injured by cluster bombs.
A report by Handicap International last week also claimed that civilians made up 98% of the casualties, in 23 countries and regions including Iraq, Afghanistan and Lebanon.
Mr Benn's letter, which is in contrast to government policy, was sent to Foreign Secretary Margaret Beckett and Defence Secretary Des Browne, the Sunday Times reported.
In it he said: "The high failure rate of many cluster munitions, and the failure of many militaries around the world to use these munitions in a targeted way means that cluster munitions have a very serious humanitarian impact, pushing at the boundaries of international humanitarian law.
"It is difficult then to see how we can hold so prominent a position against landmines, yet somehow continue to advocate that use of cluster munitions is acceptable."
The UK should lead the way in boycotting the weapons, he said, and ministers should call for a ban next week when attending a major international arms convention in New York.
"I believe we should go into the conference advocating for a process that will lead to an effective ban of `dumb' cluster munitions," he added.
Mr Benn intends to run for Labour's deputy leadership
Current government policy is that cluster munitions play a "legitimate" role in modern warfare.
The unexploded artillery are considered to be effective in targeting airfields and bases.
Ministers admitted that coalition forces used cluster bombs in built-up areas during the Iraq war, but they said a concerted clean-up operation was undertaken.
The US, Russia and China have also said they oppose a ban.