Saudi Arabia has responded to the breakdown of UN peace talks by relaunching its offensive to capture the crucial Yemen port city of Hodeidah, claiming to have killed more than 70 Houthi rebels in fighting in recent days.

On Sunday, 11 soldiers from the coalition made up of the Saudis, the UAE and local Yemeni fighters were killed, reflecting the intensity of the fighting for the strategic Red Sea port, the entry point for 80% of the aid into the country.

Aid agencies said local UN staff were reporting that the bombardment “is the worst, by far, of any since the [Red Sea] campaign started in early June,” and involves not only airstrikes and shelling but also bombardment from naval ships.

Humanitarian staff on the ground reported an “almost continuous presence of Saudi/UAE coalition aircraft” over Hodeidah since Friday night.

The coalition aim seemed to be to cut off the main supply road from Hodeidah to the capital, Sana’a.

The bulk of the fighting is on the southern edge of the city with the coalition advance led by the Amaliqa brigades, a section of the Yemeni army supplied with Emirati equipment.

The UN and Britain had invested heavily in the success of peace talks led byUN special envoy Martin Griffiths, but the talks collapsed before they started when the Houthi negotiating team said it had not received satisfactory guarantees from Saudi Arabia about its safe passage to Switzerland. Griffiths said he would continue to his efforts to relaunch the talks.

Before summer, the Saudi coalition launched and then postponed an attack on the city after the aid agencies and the UN urged Riyadh to give peace talks a chance.

The Saudi-led coalition had also been put on the back foot politically after three separate airstrikes in August killed more than 100 civilians. Saudi Arabia has subsequently admitted one of the raids was a mistake for which it has expressed regret.

But it appears that Saudi Arabia and the United Arab Emirates have concluded that the UN diplomatic track has been exhausted.

The renewed attack on Hodeidah again risks cutting off the supply of aid to Yemen. It also places pressure on the west to decide whether to remain invested in the peace talks, or implicitly back Saudi Arabia’s return to military methods.

Tory MP Tom Tugendhat, chair of the UK foreign affairs select committee, warned that the Saudi-led forces were making a strategic mistake by seeking to capture Hodeidah, warning that it could endanger Red Sea shipping.

He said forces of the Saudi-led coalition were not equipped to act as a civilian administrator in Hodeidah. “It is simply a fact that governing cities is not what armies are trained for,”he warned.

In reference to the civilian casualties caused by airstrikes, Tugendhat said the Saudi-led coalition had to review its targeting procedures, and urged it “not to sow the seeds of hate”. “You are beginning to lose the support of the US Senate, the people in this country [the UK] and you have already lost the support of many in Germany and Spain. You need to reform the way you act,” he said.

But the Tory MP Crispin Blunt, a former chair of the foreign affairs select committee, insisted that Hodeidah was “the vital ground in this conflict” because the Houthi’s main supply line into the port was being cut off. Blunt said Houthi control of the port sustained their finances, and hence their rebellion. “If Hodeidah is secured by the coalition, the conflict will be on the way to being sorted. It is our responsibility to help the coalition to deliver that objective.”

However, the former international development secretary Andrew Mitchell predicted the coalition forces would be humiliated in its efforts to take Hodeidah, calling it “an entirely crackers, bonkers strategy”.

Alistair Burt, the Middle East minister, said the UK government would support the renewal of a mandate for the UN panel of experts on Yemen when the issue is discussed at the UN human rights council later this month.