US-UK airstrikes in Yemen designed to end the Houthi disruption of commercial shipping have not seriously degraded the group’s military capability, the vice-chair of the UN-recognised government in Yemen has said.

Aidarous al-Zubaidi told the Guardian in an interview he feared the Houthis were using the strikes to rally support behind their cause by portraying the west as the aggressor in Yemen.

Calling for a change to a better coordinated strategy between the west, the region and the Yemeni government, he said it was time to accept that the Houthis were not interested in a power-sharing deal in the country – an offer made to them more than a year ago, first by Saudi Arabia and then the UN.

Zubaidi heads Yemen’s separatist Southern Transitional Council, which holds three seats on the eight-strong Presidential Leadership Council, the Aden-based coalition government opposed to the Houthis.

The Houthis are an Iran-backed group that swept to power in the Yemeni capital, Sana’a, a decade ago, driving Saudi-backed forces south towards Aden where they set up their headquarters. They began aerial drone and missile strikes on the Red Sea in November in what they said was solidarity with Palestinians in the war between Israel and Hamas militants in the Gaza Strip.

Commercial shipping companies that normally use the Red Sea have been forced to take long and expensive detours around the Cape of Good Hope and to accept higher insurance costs. Operation Prosperity Guardian was established in December largely by the US and UK to protect shipping and strike back at the Houthis.

Zubaidi said: “The airstrikes, instead of deterring the Houthis, are having the opposite effect. In a way, it is helping the Houthis and making them stronger. The local popular perception is that the Houthis occupy the high ground because they are mobilising people around the idea they are being attacked by the UK and the US, and the Houthis are mounting a defence.

“What is more, these operations are not really effective militarily. The Arab coalition, one way or another, has been attacking Houthi rocket launchers for the past eight years, but the Houthis have been able to adapt and find new solutions on how to hide their capabilities. They have built up resilience. The problem is [there is] no joined up approach involving the region and Presidential Leadership Council. It is a US-British operation alone.

“It’s clear that at the Red Sea ports of Hodeidah and Salif, ships have been arriving without inspection containing high quality weapons from both the Iranians and Russians.”

The deliveries had given the Houthis the capability to target Israel, he said.

The negative assessment of the impact of Operation Prosperity Guardian from a Yemeni group so opposed to the Houthis will not be easy to dismiss.

“Events over the past year require a shift in thinking. The past peace process is no longer viable,” said Zubaidi, who is in New York as a member of the Yemen government delegation to the UN general assembly. “The Houthis now regard themselves as the state in Yemen and do not recognise the government in Aden, and say they only want to talk to the west.”

He said that after a decade in power the Houthis had indoctrinated a younger generation into its narrow sectarian ideology. “There is not likely to be an internal counter-revolution against the Houthis soon,” he said.

A coordinated international, regional and local strategy to contain and weaken the Houthis was needed, requiring political, military and economic tracks, he said. That must include a strategy to start re-exporting oil and building national revenues independent of Saudi grants, he said.

He conceded that the Presidential Leadership Council assembled by the Saudis in April 2022 was politically divided, lacked proper procedural rules and needed reform.