The Middle East’s polarised and repressive politics will lead to even more instability in the region unless countries take steps to reform and calm tensions, a senior Qatari politician has said.

Mohammed bin Abdulrahman al-Thani, Qatar’s deputy prime minister and foreign minister, urged international powers including the US to be more inclusive in their approach to the region, saying one-sided initiatives that excluded either the Iranians or Palestinians did not work.

“Anyone that looks at the situation right now – the polarisation in the region – is quite certain that things will not remain like this,” Thani said. “You cannot keep people under oppression for a long time, so to prevent this instability from happening, we just want leaders to start reforming. We have to practice preventative diplomacy rather than reactive diplomacy.”

He called on Saudi Arabia to cooperate with the inquiry set up by the UN to look into the death of the Washington Post columnist Jamal Khashoggi.

Qatar has been on the receiving end of an economic, diplomatic and political boycott by Saudi Arabia, Egypt, the United Arab Emirates and Bahrain, stretching back to June 2017. Those countries accuse Qatar of funding extremist groups and being too close to Iran – allegations Qatar denies. The Qatari government consider itself a benefactor and mediator, offering its territory as the UN’s sub-station in the middle east. The country, which has a $300bn (£230bn) sovereign wealth fund and large gas reserves, hopes hosting the football world cup in 2022 will boost its prestige on the international stage.

As well as acting as a mediator with the Taliban, Qatar has, according to Thani, provided more than $1bn in help to alleviate suffering in Gaza and spent $500m to stabilise the Lebanese economy, a country previously seen as domain of the Saudis. More recently, it has been extending its reach into African and Asian markets.

Unlike most other Gulf states, Qatar has continued to support the Iran nuclear deal, distancing itself from the anti-Iranian axis of the US, Saudi Arabia and Israel. “Our position on the Iran deal is that, like the Europeans, we support it,” Thani said. “We do not want a nuclear arms race in our region, and that is the danger.”

He insisted this did not mean his country had now, as some claimed, formed a new axis with Iran and Turkey. “Our geography is difficult. We have sided with no one. It’s not easy to be a facilitator for talks between adversaries.

“If you look at the core of the issue, the Gulf Cooperation Council [the six-member group of Gulf States] needs to reach an understanding with Iran, not just Saudi Arabia and Iran – all of us are living in the same neighbourhood and we need to reach an understanding. That was the common position of the GCC countries until 2017, but the boycott changed everything.”

He said he had spoken to Jared Kushner, Donald Trump’s middle east advisor, who told him his much-delayed Israel-Palestine peace plan for the region would be “ready in a few weeks”. Qatar, Thani insisted, “had no interest in anything that is not a two-state solution, 1967 borders, the right of return, clear designation of Jerusalem as the capital of Palestine”.

Thani reserved some of his harshest judgements for the Khashoggi assassination, which the CIA has concluded was probably ordered by the Saudi crown prince, Mohammed bin Salman. “What has happened was a brutal crime,” Thani said. “The family of Khashoggi needs answers and needs to be able to identify what happened to their father. There has to be accountability for what happened. Dealing with political opposition through crimes is wrong.”

Although he said it was not for him to judge the legal process of other countries, he said he hoped Saudi Arabia would cooperate with the UN inquiry into the death. “Since the UN inquiry is an international process under international law, everyone should co-operate,” he said.

As to Qatar’s own democratic progress, Thani said his country – ruled by a monarch – was slowly evolving, with imminent parliamentary elections. “We cannot replicate the model of western democracy 100%,” he said. “We have different customs and models, but we are taking significant steps”.