British forces have succeeded in dropping humanitarian supplies to Yazidi refugees besieged by forces from the Islamic State (Isis) on Mount Sinjar in northern Iraq.

Justine Greening, the international development secretary, said the RAF had dropped "essential supplies" of water and rechargeable solar lanterns.

The successful mission came 24 hours after the crew of an RAF C130 Hercules had to abort two missions on Sunday night amid fears that the cargo could have injured people on the ground.

Britain announced on Monday that it would deploy RAF Tornado jets to provide greater surveillance for the crews dropping humanitarian supplies. The deployment came amid growing calls for a recall of parliament to allow Britain to join the US in launching air strikes against forces from Isis.

Mark Pritchard, the Conservative backbencher, became the latest MP to join an informal cross-party coalition led by the former Labour foreign secretary Jack Straw and the former Tory armed forces minister Andrew Robathan calling for Britain to step up its involvement.

Pritchard wrote on the PoliticsHome website: "The international community can pour as much aid into the region as it likes. But unless Islamic State fighters are killed and removed from the battlefield, they will go on killing and committing further atrocities.

"The UK must not walk by on the other side and that is why overnight news that RAF Tornados are once again going to fly in Iraqi airspace is welcome. However, this intervention needs to be in an unequivocal combat role, not just in an intelligence, surveillance and targeting role."

Straw welcomed the plan to deploy Tornados. But officials made it clear that the Tornados, whose actual deployment over Iraq has yet to be agreed by ministers, would be used solely for surveillance to avoid a repeat of Sunday night, when the crew of an RAF C-130 Hercules aircraft had to abort their mission to avoid injuring refugees on the ground.

Philip Hammond, the foreign secretary, who chaired a meeting of the government's emergency Cobra committee, insisted that Britain was only providing humanitarian support and would not join the US in launching military strikes against Isis forces. Downing Street indicated that Britain might be prepared to follow the example of the US in arming Kurdish forces that are fighting Isis, though the prime minister's spokeswoman said no decision had been taken.

But the cross-party coalition of MPs is calling for Britain to join the US strikes against Isis forces. Straw, who said parliament might have to be called to discuss the crisis, told ITV News: "I hope that the British government are now accelerating their humanitarian intervention and assistance. It's taking a bit of time to get going and these poor devils are dying at the moment.

"They have to look at what further action we could take by way of military assistance. Not talking about boots on the ground; there are other things we could do. One way or another, these maniacs, these medieval maniacs, in the so-called Islamic State, have got to be defeated."

Robathan said Britain would have to be involved in military strikes if it wanted to defeat Isis forces. He told the World at One on BBC Radio 4: "There can be no real help for the people of Iraq that are threatened by [Isis] without stopping [its] advance. That is what anybody who is worried about the humanitarian situation has to admit.

"We have to realise it is no good just sending aid. The real solution is to stop these people and hopefully allow the Iraqis and the Kurds to defeat them. There are many ways one could use military strikes – air strikes or the use of drones can be done fairly surgically without putting troops on the ground. We had our fingers pretty badly burned in Iraq, as did the Americans.

"There is no appetite to have proper troops on the ground. However, the idea of a few observers perhaps directing air operations is a slightly different matter."

Downing Street joined Hammond in ruling out British military involvement though the prime minister's spokeswoman indicated that Britain might be willing to follow the example of the US in arming Kurdish forces. The spokeswoman said: "Our focus is on the humanitarian effort. We do think it is important that the Iraqi forces, including the Kurdish forces, are able to respond to Isil [Isis] and to tackle this crisis. So we will look at what options there are that might enable them to do that. But there have not been discussions, substantive discussions, of that yet. There are certainly no decisions."

The prime minister has ruled out British military involvement in Iraq amid strong public resistance to renewed action. Cameron was also bruised when he recalled parliament during last summer's recess to approve military action against Bashar al-Assad after the Syrian regime's chemical weapons attacks on a Damascus suburb. The prime minister was defeated after a Tory rebellion and the refusal of Ed Miliband to agree to an amended government motion. Cameron decided after the vote that it would be all but impossible to secure the support of MPs for military action in this parliament.

The decision to deploy the Tornados to the region came as Britain proposed a UN security council resolution to punish the recruitment and financing of fighters for Isis. An early draft of the resolution, seen by the Associated Press, says that "widespread or systematic attacks directed against any civilian populations because of their ethnic background, religion or belief may constitute a crime against humanity".