PJ Harvey has released a new song to highlight the ongoing detention of the last British resident held inside the US prison at Guantánamo Bay.

The track, called Shaker Aamer, is available to stream exclusively on our website and was recorded by the Mercury prizewinning songwriter to help maintain pressure to have the 46-year-old, whose family live in south London, released back to Britain.

Aamer has been detained in Guantánamo for more than 11 years, despite being cleared for release in 2007, and remains imprisoned without charge or trial. He has a British wife and his four children – the youngest of whom he has never met – were all born in Britain. They live in Tooting, south London.

The British government has stated repeatedly that it wants him back in the UK and last week, under escalating international pressure, the US announced it is to restart transfers from the prison. Concerns remain, however, that Aamer might be forcibly sent to Saudi Arabia and imprisoned there instead of being reunited with his family in the UK.

More than half the detainees inside Guantánamo Bay remain on hunger strike in protest at their indefinite and illegal detention. Aamer recently alleged that prison guards have been sexually assaulting him and that he is subject daily to often violent "forced cell extractions".

Harvey's lyrics recount the suffering of Aamer on hunger strike – which he has been on for four months now – articulating his loss of dignity and likening himself to an "old car, rusting away". The final lyrics of the song are simply "Don't forget".

Clive Stafford Smith, Reprieve's director and Aamer's lawyer, said: "We hope people listen to this song and think about Shaker Aamer's plight: detained for 11 years, without charge or trial – despite having been cleared for release by both Bush and Obama.

"The UK government must do everything it can to bring Shaker back home to his wife and kids in London, where he belongs. PJ Harvey has written a wonderful song – I know Shaker will be deeply moved by it, and I only hope that, with the support of the public, he will one day be able to listen to it in freedom."

PJ Harvey's last album, Let England Shake, explored the horrors of war and helped cement her position in the British rock establishment. She is the first ever double Mercury prizewinner.