Since 1967, more than 730,000 Palestinian men, women and children are estimated to have been imprisoned by Israeli military courts. The majority of such prisoners are held in detention facilities inside Israel, in violation of the Fourth Geneva Convention, which prohibits the transfer of these prisoners into Israel.

The practical consequence of this violation is that many prisoners, including children, receive either limited or no family visits, due to freedom of movement restrictions. In the case of children, this lack of adequate family contact also violates their rights under article 37 of the Convention on the Rights of the Child.

According to Israeli Prison Service figures released in June of this year, 85 per cent of Palestinian prisoners, including children, were detained inside Israel. Of 4,706 prisoners, 285 were held in administrative detention, without charge or trial.

The UK government has confirmed that Israel's policy of detaining Palestinians is contrary to Article 76 of the Fourth Geneva Convention, that they have raised this with the Israeli government and will continue to do so. In a recent letter to me, Foreign Office Minister Alistair Burt MP stated that the FCO is lobbying Israeli authorities for a number of improvements, including a reduction in the number of arrests that occur at night, an end to shackling and the introduction of audio-visual recording of interrogations.

Such diplomatic pressure is important - but what of the British companies that keep Israel's prisons running? According to corporate accountability campaigners, the security giant G4S, which is listed on the London Stock Exchange, signed a contract with the Israeli Prison Authority in 2007 to provide services to a number of prisons and detention facilities. Some of these are known to house prisoners transferred from the West Bank.

What's more, the company has installed a central command room in Ofer Prison in the occupied West Bank, which houses a centre where prisoners are tried under military law. Ofer Prison is located in what the Israeli military refers to as the "Seam Zone", which means access for visiting families is highly restricted.

G4S have said that it will exit from all the contracts it holds in the West Bank at the earliest opportunity the contract terms allow. They also say that they have not violated any international laws, which on this specific issue may be correct, given that the Geneva Conventions apply only to Governments that have ratified their terms. Despite these limitations, the UK government can still act - yet it refuses to.

Alastair Burt told me that, despite being aware of G4S's involvement in Israeli prisons, the Foreign Office has not discussed the issue with the company and believes that the "provision of services in Israel and the Occupied Palestinian Territories is a matter for G4S."

Last June the UK Government co-sponsored a UN resolution that places duties on states to protect against corporate abuse of human rights. The commitment is meaningless if the government refuses to take action in a clear-cut case such as this.

Companies that have been involved in grievous human rights abuse continue to be listed on the London Stock Exchange, seriously damaging the reputation of British business abroad and making it more difficult to compete for those businesses which are trying to uphold high ethical business and trade standards. Such abuse by any corporation is not merely a matter for the company, but for everyone who supports and believes in the basic concept of human rights.

Lisa Nandy is Labour MP for Wigan and Chair of the All Party Parliamentary Group on International Corporate Responsibility