MPs are calling for a full account of arms exports to Israel amid growing concerns that British military equipment was used during the bombardment of Gaza – contrary to Israeli assurances and UK export guidelines.

The government was adamant UK exports were not used in drone aircraft that helped the Israeli air force target missile strikes that killed more than 1,000 people and demolished thousands of homes and other buildings and infrastructure.

Now, however, ministers say they are unsure what equipment was used. Attention has been focused on two critical weapons in Israel's frontline forces: the F16 ground attack fighters and the Hermes 450 drones, which pinpoint the sites for attack.

British arms control officials have admitted they are unable to say whether UK-made aircraft engines were fitted to drones. And ministers say they have been unable to ascertain whether the planes were fitted with the pilots' electronic kit for launching missiles, which was controversially – but legally – sold by BAE Systems to Israel, via the US, in 2002.

MPs on the joint committee currently examining arms controls have expressed their frustration at the lack of information. At a hearing, they also complained that for three months the foreign office had failed to respond to questions about UK equipment in the naval blockade of Gaza last year.

A Labour member of the committee, Richard Burden, who is also chairman of the Britain-Palestine parliamentary group, told the Guardian the government should provide "chapter and verse" on the use of all British arms exports to Israel, including critical components for the F16s.

"It should be possible for the government to establish the end-use of these exports. And if they cannot do that through independent checks, then that suggests that Israel is not a reliable trading partner for arms and components," he said.

He recalled that in 2002 Israel was found to have broken its written assurance that no UK equipment would be used in the occupied territories when it was disclosed that Centurion tanks had been converted by the IDF into armoured personnel carriers.

Describing Israel as a "country of concern", the UK says it refuses to export military goods that can be used for internal repression or external aggression.

The foreign secretary, David Miliband, has twice been challenged on the issue of the engine drones in the Commons since Amnesty International and the Guardian three weeks ago pointed to evidence suggesting engines made by an Israeli-owned factory in Staffordshire had been fitted to the Hermes 450 unmanned aerial vehicle. .

Miliband told MPs who have been calling for an arms embargo the allegations were false. The engine, he said, "was not being used by the IDF but had in fact been for export. I am happy to stick with that."

The Israeli company that imported the engines, Elbit Systems – the owners of the British manufacturers UAV Engines Ltd (UEL) – has denied they were fitted to military drones in Israel, saying they were incorporated into aircraft for export only to third countries.

But at the committee hearing Jane Carpenter, a senior official with the export control section of the business and enterprise department, said that had not been checked. Sitting with Ian Pearson, the responsible business and enterprise minister, Carpenter said: "We cannot categorically confirm that we have physically checked that the engines have been incorporated. We only licensed them to Israel for onward export."

She added that, had the engines stayed in Israel, "that would be a contravention of the licence condition, and that would be an offence".

Pearson explained what checks had been made to allow Miliband to deny the allegations. "My understanding is, we have spoken to this exporter and they have confirmed what we already know from our own database: that while they export UAV engines to Israel, the engines are a particular variant which is not used in Israel but is incorporated into UAVs for onward export. So they would not have been involved in the current conflict."

Pearson also said that the UK government had no clear idea whether the F16s had used the BAE Systems gunsight technology.

Israel is a major exporter of UAVs, and the Hermes 450 has been sold to the US, Singapore and Georgia.

Britain's sensitivity about its military relations with Israel are acute since the Hermes is also the basis for the drone being developed by Elbit and the French company Thales for the £900m Watchkeeper UAV programme for the British army. The UK version, fitted with UEL engines, is due in service next year.

The Hermes programme , like all the Israeli-developed drones, is classified as a state secret; the IDF has refused to confirm or deny reports, which first surfaced during the second Lebanon war in 2006, that they were armed with missiles.

The evidence accumulated by the Guardian and Amnesty from academic and specialist aerospace public sources, as well as from Elbit's website and filings to the US security and exchange commission, suggested that the IDF Hermes had used engines made in the UK. The IDF first acquired these in 1997, three years after UEL Engines was bought by Elbit's drone subsidiary, Silver Arrow.

The authoritative industry journal Jane's Defence Weekly reported at the time: "It is powered by a 52 hp UEL AR-80 1010 rotary engine with propeller." Despite repeated requests, government departments have been unable to say whether they know what engines are used on the IDF's drones.

Oliver Sprague, Amnesty International's UK arms control programme director, said: "Available evidence suggests these drones are powered by UK engines. Until someone from the UK government goes and physically inspects the drones, it's hard to see on what basis they are dismissing these serious allegations."

"Until a robust system of end-use monitoring is in place, the UK will forever be reliant on assurances from other countries, and from arms companies, that British-made equipment is not being used to abuse human rights."