As Britain’s foreign secretary warns of “a shortening window of opportunity” for peace in Yemen, the hours are also counting down for weapons manufacturer Raytheon UK to explain its activities to the government’s committees on arms export control (CAEC).

Raytheon, the world’s third largest manufacturer, was called upon to give live evidence on Wednesday. However, the company has effectively avoided face-to-face scrutiny by simply declining to attend.

Raytheon is not alone. A precedent was set last year when British secretaries of state also failed to appear before the watchdog. Such conduct raises questions about CAEC’s accountability and effectiveness.

The body, which consists of representatives from thedefence, foreign, business and enterprise, and international development select committees, is charged with policing the government’s arms export strategy.

Committee members want to raise questions over UK involvement in Yemen and the supply of weapons to the Saudi-led coalition. But the refusal of Raytheon UK to appear potentially limits the committee’s ability to establish what steps are being taken by manufacturers to avoid misuse and diversion of supplied arms, once export applications have been authorised by the government.

While they are not directly responsible for human rights abuses by end users, manufacturers have a moral duty to reduce the likelihood of their weapons being put to such use.

Raytheon are manufacturers of the Paveway IV, a laser-guided smart bomb that has been used with devastating effect in Yemen. An investigation by civil rights charity Mwatana has established that the bombs were among those dropped during 27 allegedly unlawful Saudi-led coalition airstrikes that took place in Yemen between April 2015 and April 2018, killing civilians and destroying infrastructure including schools and hospitals. Amnesty International are among those who say such conduct breaches international humanitarian law. That view is not necessarily shared by Graham Jones, the CAEC chair, who last month remarked of NGO reporting on the impact of airstrikes” “We see it time and time again with regards to airstrikes – there is a gross exaggeration by NGOs as to what has happened.”

Raytheon UK employs more than 1,500 UK staff and describes itself as a “prime contractor and major supplier to the UK Ministry of Defence”. In 2017, it generated £461m in sales and more than £700m for UK GDP. In 2018, its parent company in the US, Raytheon, forecasted its annual turnover to be between $27bn and $27.3bn, alongside an order backlog of $41.6bn.

Confirming Raytheon UK’s non-appearance, Jones said “I’ve asked NGOs, academia etc, ministers and arms manufacturers to appear. Raytheon UK have declined.”

The Guardian understands that Raytheon UK has notified Jones that ADS Group, a trade organisation that represents UK companies operating in the aerospace, defence, security and space sectors, will answer questions on its behalf. ADS, whose website says “influencing policy debates” is among its key functions, had already been invited to give “general industry evidence”.

But Raytheon UK’s decision to abstain from the inquiry carries with it far more serious ramifications for this year’s inquiry. It potentially reduces the effectiveness with which the committee can examine the company’s relationship with UK and other governments as well as its ability to explore details about the quantity and types of weaponry being supplied under the open licence system, which the committee has previously criticised for a lack of transparency.

Save for ADP, the only other body that will attend today’s hearing is Make-UK, industry representatives who describe their role as to “stimulate success for manufacturing businesses, helping them to meet their objectives and goals”.

Raytheon’s refusal comes at a time when academics are questioning CAEC’s ability to hold the government to account over its seemingly endless authorisations for the supply of weapons to countries with dubious human rights records, like Saudi Arabia.

CEAC’s own calls for transparency – following its review of 2016 arms exports – all but fell on deaf ears. The government rejected many of its proposals, continuing to suggest that the UK already operates one of the most robust export control regimes in the world.

At CAEC’s first session, held just six weeks ago, international charities providing aid to conflict zones raised issues about the accountability and transparency surrounding UK arms export policy. Criticism was later levelled at the committee for failing to address Yemen, despite mounting evidence suggesting that the government’s continued authorisations for the supply of arms to the zone are in breach of its own rules as well as international humanitarian law.

However, Raytheon is not alone in declining CAEC’s invitations over the course of this parliament. In several cases, it is unclear whether non-attendance forms a course of conduct by those involved in the decision-making process of arms export, or whether it effectively amounts to contempt or a passive disregard for the committee’s authority. It is a subject worthy of debate.

Last year’s review of arms exports in 2016 was attended by BAE Systems and Leonardo. However, Smith Myers, manufacturers of dual-use sensitive communications equipment, declined to appear before the committee. They potentially faced far-reaching questions after reports by Privacy International, a watchdog, alleged that the company was involved in the supply of portable Imsi-catchers – devices that intercept mobile communications – to repressive regimes/security services including Colombia.

Likewise secretaries of state. Boris Johnson, foreign secretary at the time, and Liam Fox, the international trade secretary, failed to attend last year’s final evidence session, sending along ministers instead.Jones questioned the non-attendance, pointing out that the session had been convened to accommodate their availability with four weeks’ notice.

The ministers duly apologised, insisting they took the role of the committee seriously. Sir Alan Duncan, minister of state for Europe and the Americas, commented in his apology: “I’m sorry if you feel you have the monkey rather than the organ grinder.”

Whilst the ministers were able to answer some questions, others had to be deferred, including the government’s inability to stop 30m rounds of ammunition being supplied to Saudi Arabia, despite being in possession of intelligence suggesting that the consignment was at significant risk of being diverted to third-party groups.

Explaining their decision to decline CAEC’s invitation, a spokesperson for Raytheon UK said: “Raytheon did not refuse to attend the CAEC session. Raytheon, like all members of our trade association, is being represented by ADS in matters of government policy.”

Smith Myers acknowledged receipt of an approach for comment from the Guardian, but failed to respond.

Jones did not comment on Raytheon’s non-attendance. Nor did he comment on allegations that CAEC, in its current form, is ineffective and needs restructuring in order to gain compliance from all parties.

However, committee member Lloyd Russell-Moyle said: “Raytheon, the main British exporter of missiles to Saudi Arabia, has refused to face parliamentary scrutiny. Its bombs have been found in hospitals, weddings, funerals, factories and other civilian cites across Yemen, in clear violation of international humanitarian law. The high court judged the executive can licence Raytheon bombs to Saudi Arabia in part because it is scrutinised by CAEC; we cannot scrutinise if Raytheon does not turn up.”

At the conclusion of the committee’s session on Wednesday evening, Raytheon will be off the hook for another year. The committee will want to hear from the secretaries of state at their next sitting in a few weeks time. The question is, who will present themselves?