A proposal to ban firearms that can be converted into handguns faces a vote in the European Parliament.
Police say converted handguns are finding their way on to the streets
British MEP Arlene McCarthy, who is behind the campaign, says the supply of guns to criminals has to be tackled.
The parliament in Brussels will also consider a proposal to raise the age for obtaining firearms to 18.
Earlier this month, a student shot dead eight people at a school in Finland, where gun ownership is among the highest in the world.
Ms McCarthy started her campaign when she discovered that almost half the weapons seized by Greater Manchester Police in 2006 had been converted after being imported from countries such as Germany or Lithuania as alarm guns, gas guns or blank-firing guns.
Twelve-year-old Kamilah Peniston was fatally shot at her home in Manchester while her brother was playing with a converted gun.
Ms McCarthy said she had convinced member states as well as the commission to include the proposal in its original directive which, if passed, would have to come into force across the EU by 2010.
A ban on handguns was introduced in the UK after the murders of 16 schoolchildren and their teacher at Dunblane, but that has not stopped the convertible guns entering the country.
With the third-biggest gun-ownership in the world, Finland has been reluctant to change its laws.
But public opinion changed after the shooting at a school in Tuusula.
Finland has already announced it is prepared to increase the age for acquiring firearms to 18, although critics have pointed out that the gunman involved in the school killings had already turned 18.
Pekka-Eric Auvinen carried out his killings armed with a pistol for which he had been given a licence only weeks before.
Because his gun was licensed and he was over 18, Finnish MEP Ville Itala is not convinced the new directive would have prevented the murders in his home country.
A former police chief in Finland, Mr Itala says the problem lies not with his country's laws but in their implementation.
"I'm not sure [Arlene McCarthy's] amendment will be helpful. From my own point of view, it was a mistake that police hadn't looked into his background," he says.
Ms McCarthy acknowledges that it will always be difficult to stop people getting hold of guns if they are determined.
But she says that anyone with a criminal or a mentally unstable background should face checks.
The new proposals will "control the smuggling of weapons and put in controls for legal weapons", she said.