The reputation of British politicians is at a “low point”, the UK’s new independent parliamentary commissioner for standards has said, as he pledged to be an advocate for the “vast majority” of MPs who were committed to high standards in public life. Daniel Greenberg, who takes over from Kathryn Stone when her five-year term comes to an end in January, admitted that a slew of scandals in recent years as well as the turbulence of the past 12 months had tarnished parliament’s reputation. In his first interview since being appointed, the barrister and legal expert said: “It’s a low point within recent decades. It’s definitely a low point in the reputation of politics and politicians … I think politicians as a class definitely have made some mistakes.” However, he added: “The reputation isn’t always deserved … We’ve had some very significant, high-profile and very serious cases of breach of standards in the past five or so years. But in terms of numbers, we’ve got 650 MPs and the vast majority have strong commitment to high standards in public life.” Greenberg will be the seventh commissioner, employed by parliament rather than the government to safeguard independence, since the post was created in 1995. He pledged to conduct his new role “without fear or favour” and to investigate whoever needed to be investigated, from backbench MPs to prime ministers. Yet he also hopes to focus on the “positive” side of the job – giving guidance and support to MPs and outreach work with the public. His years of parliamentary experience “put me in a good position to support the best and to be critical of the worst”, he said. “I have a deep emotional attachment to the place and what it represents. That’s why I wanted to do [the job], because it upsets me that parliament gets a less impressive reputation than it often deserves. When you see the low level of trust between the public and parliament, politicians at all levels, you want to get involved.” Greenberg, an orthodox Jew, was born and brought up in north-west London and educated at Trinity College, Cambridge. The 57-year-old has spent 35 years working in parliament, including drafting and scrutinising legislation, and is counsel for domestic legislation in the Commons. His predecessor provoked the ire of Conservative MPs when she published a highly critical report into the former cabinet minister Owen Paterson over lobbying. Boris Johnson’s intervention in the scandal was a tipping point in the former prime minister’s public standing. Greenberg said he would not hold back from investigating any politician for wrongdoing, regardless of seniority. “My role over 35 years has been to give my opinion without fear or favour. I’ve said no, or even worse things, to ministers on many occasions. In that respect, I think this will be a natural continuation of my experience.” He also had a warning for MPs after Chris Bryant, the chair of the cross-party standards committee – which polices their conduct – revealed that some were lobbying on behalf of colleagues. The new commissioner said he would “take that very seriously” if it happened as it could “undermine” the independence of the system. Greenberg admitted the number of different standards bodies – including his own, parliament’s independent complaints and grievance system and the prime minister’s adviser on ministerial interests – could be confusing for the public but said each had to be able to “get on with” their own role. However, he indicated that Rishi Sunak should crack on with filling the ethics adviser role that has been empty since Christopher Geidt quit in June, a day after admitting “frustration” over Johnson’s role in the Partygate scandal. “They’ve said they’re going to do it, and although the considerations involved with ministerial standards are significantly different from MPs’, it is a role I look forward to liaising with. In terms of coherence for the public, it will be very good to have that filled,” he said. Greenberg also intends to hold the government to its promise to back plans to crack down on MPs’ second jobs. “Do I have a role in making sure this doesn’t get kicked into the long grass? Yes, I do,” he said. “It shouldn’t be in the long grass … It’s a serious question because it goes to the heart of reputation and integrity.” However, he said there was not a “single, simple answer” to whether MPs should have outside interests. “There is a value in members having a continuing experience outside the House – and there are dangers in members either having too many, or conflicting, roles outside the House. It is a balance that needs to be struck.”