A US serviceman stands by an unmanned drone. the use of the machines has been condemned by human rights groups as an example of extra-judicial assassination.

Barred: Home Office prevents drone victims visiting parliament

Barred: Home Office prevents drone victims visiting parliament

The Home Office has prevented a parliamentary meeting on drone strikes going ahead after it refused visas to victims.

Noor Khan, Kareem Khan and Noor Behram are now unable to attend a parliamentary meeting hosted by Labour MP Tom Watson tabled for today.

"It is an unfortunate coincidence that David Cameron is refusing to grant a visa to the very same man who is suing his government over its role in the drone strike that killed his father," Cori Crider, strategic director at human rights group Reprieve, said.

"Just last week the Rehmanfamily were able to tell their story to the US, yet the UK seems unwilling to extend a similar courtesy to these three victims of the drone programme. The British government must reconsider and grant the men visas."

The Home Office's refusal to allow the men into Britain is particularly surprising given the Rehman family travelled to Washington recently to speak about drone strikes after being granted visas by US authorities.

The trio's visa applications were backed by letters to the Home Office from Watson.

"It's very disappointing that visas have not been granted in time for the drone victims invited by the APPG [all party parliamentary group] on drones to speak today," Watson said.

"Last week the Rehman family travelled to the US and testified to Congress about their grandmother who was killed by a CIA drone. The UK must allow Noor Khan and other survivors into the country so that we too can hear these lost voices."

Noor Khan is suing the British government for sharing information with the US which was used in drone strikes.

He was going to be accompanied by Kareem Khan, whose son and brother were killed in a drone strike on New Years Eve 2009. He is suing Jonathan Banks, former CIA station chief in Paistan, and John Rizzo, former CIA general counsel.

Behram is a journalist who has been investigating and photographing drone strikes in the tribal areas of Pakistan for almost six years.