Liz Truss will be advised by Buckingham Palace not to present a long list of resignation honours after her short and disastrous premiership, according to senior figures with experience of the system. One source with close knowledge of honours protocol told the Observer that, given her time in No 10 lasted just seven weeks and was marred by economic crisis and U-turns, rewarding lots of allies and friends would be seen as inappropriate by the Palace, by cabinet secretary Simon Case and almost certainly by the new prime minister, Rishi Sunak. “These things are done in a very British way,” said the source. “I think it will be clear that this would not be right. It will a be a case of … you don’t want to embarrass the king, do you? “This situation is completely unprecedented. I am sure a lot of people will be saying to Liz you can have an honours list but it has to be a pretty small, not everyone in your office, not what David Cameron did. He added: “She was a bona fide prime minister. She can do it but there will be a lot of pressure on her from the Palace, from the Cabinet Office, saying keep the numbers down, not using it to give out honours to lots of people. Simon Case would be saying, ‘Do it but don’t go mad.’” Another senior figure who has served at the highest levels in Whitehall said there was no doubt that Truss, having been rightfully chosen and served as prime minister, had a right to draw up a resignation honours list, and that her successor – in this case, Sunak – would not be expected to stand in her way. While there are no formal rules, the system is governed by convention which dictates that whatever is proposed by an outgoing prime minister would be expected to be unopposed by his or her successor. But the senior Whitehall figure added: “I think people would be having a word with the prime minister to make clear that in this case he should be making clear it that had to be quite modest. There would discussions. Ultimately they are in the gift or the monarchs and there would be lots of discussions.” Since Truss left office last Tuesday, there have been rumours about the names on a potential Truss list, and suggestions that she may want to elevate her close friend and chancellor Kwasi Kwarteng, who she sacked over the mini-budget fiasco, to the House of Lords. Friends of Kwarteng deny that he would want a peerage and insist he wants to remain as an MP. With Boris Johnson yet to submit his resignation honours list after being ousted in the summer, there is growing concern among some existing peers that the upper house faces a major new influx, when the aim is to reduce numbers. When David Cameron left office in 2016 he caused disquiet by giving honours to large numbers of his staff. His successor, Theresa May, was known to have been angered by the number and identity of the names on Cameron’s list, but concluded that she could not stand in her predecessor’s way, as this would set a dangerous precedent. Last night the government was urged to launch an urgent investigation following reports that Liz Truss’s phone was hacked. The breach was discovered when then-foreign secretary Truss was running for the Tory leadership in the summer, but details were suppressed by Boris Johnson, who was prime minister at the time, and the cabinet secretary, Simon Case, the Mail on Sunday reported. Spies suspected of working for Russian president Vladimir Putin gained access to sensitive information, including discussions about the Ukraine war with foreign officials, the newspaper said, citing unnamed sources. It also claimed that private conversations between Truss and Kwasi Kwarteng criticising Johnson fell into the hackers’ hands. Labour’s shadow home secretary, Yvette Cooper, said: “It is essential that all of these security issues are investigated and addressed at the very highest level and we need to know that the government recognises the gravity of this and the importance of fully protecting our national security.” The Liberal Democrat foreign affairs spokesperson, Layla Moran, said: “We need an urgent independent investigation to uncover the truth.”