Environmental and human rights groups have expressed outrage that the UK taxpayer spent more than £100,000 sending David Cameron to Saudi Arabia to pay his respects following the death of its king in January.

The huge sum, which dwarfs the amount spent sending the prime minister on other trips overseas, is revealed in new information released by the Cabinet Office showing the cost of all the prime minister’s trips overseas between July 2014 and March 2015. They confirm that on 24 January Cameron and four others took a charter flight to Saudi Arabia “to pay condolences following death of King Abdullah bin Abdulaziz”. The total cost of the trip to the taxpayer was listed as £101,792. In contrast, Cameron and five others flew to Australia last November to attend the G20 meetings at a cost of £13,290.

Publication of the figures comes at an awkward time for the government. The UK’s relationship with the kingdom, where capital and corporal punishment are common, is under close scrutiny after the Ministry of Justice pulled out of a £6m contract to help run Saudi prisons after pressure from human rights groups. They are concerned about the imminent execution of two men, Ali Mohammed al-Nimr and Dawoud al-Marhoon, who were juveniles when they were arrested and tortured following protests in 2012. There are also fears for British pensioner Karl Andree, 74, who has been sentenced to receive 360 lashes for possession of alcohol.

Ali Mohammed al-Nimr is set to be executed for his role in 2012 pro-democracy protests in Saudi Arabia. Photograph: Facebook

“The government is clearly going to great lengths to preserve its close relationship with Saudi Arabia,” said Maya Foa, head of the death penalty team at Reprieve. “But with a terrible human rights record that includes the planned execution of juveniles Ali al-Nimr and Dawoud al-Marhoon, it is crucial that the Saudis are strongly pressured to change course by its closest allies – the UK included. The foreign secretary said this week that he ‘did not expect’ al-Nimr to be executed, but this is not good enough. Britain must be using its obvious influence with Saudi Arabia to push strongly for the release of Ali, Dawoud and the other juveniles, and an end to the repression that saw them sentenced in the first place.”

The government’s response to the death of Abdullah drew controversy at the time. Cameron was pillioried in some quarters for declaring: “My thoughts and prayers are with the Saudi royal family and the people of the kingdom at this sad time.” Cameron defended a decision to fly the union flag at half mast, saying Saudi intelligence had saved British lives.

John Sauven, executive director of Greenpeace, whose investigation unit unearthed the overseas travel figures, said they showed the UK was prepared to ignore the human rights records of countries that could help it meet its energy needs. “We prostrate ourselves before the Saudis because they have oil, and we prostrate ourselves before the Chinese because they’ll pay for a new nuclear plant,” said Sauven.

“Meanwhile, [George] Osborne’s policies are causing the defenestration of our own domestic clean energy sector. Solar companies are going to the wall with the loss of thousands of jobs, while onshore wind projects are being blocked and cancelled despite them being the most cost-effective way of producing power. If this chancellor has a vision, it’s one of Britain supplicating before authoritarian regimes while our high-technology renewables industry goes to the wall.”

A spokesman for the prime minister declined to elaborate on why the Saudi trip cost so much more than other overseas trips. “This charter flight was for a group involving the prime minister, Downing Street officials, the royal household and protection officers,” said the spokesman. “The visit was to pay condolences following the death of the king, which was attended by heads of state from across the world.”