Ministers are to face further questions over the decision to allow the export of substances used to make chemical weapons to Syria, months after the country descended into civil war.

In a letter to the business secretary, Vince Cable, to be sent on Monday, a member of the House of Commons' committee on arms export controls will demand to know who was allowed to sell the chemicals and what other licences for the export of dangerous materials to Syria have been granted.

Labour MP Thomas Docherty will also ask which civil servants knew that the potassium fluoride and sodium fluoride they allowed British firms to sell could be used to make nerve agents and when they found out.

Docherty criticised the government after it emerged that British firms were granted the licences in January 2012, about 10 months after the start of the bloody conflict. In a draft of the letter, seen by the Guardian, he wrote that he was "horrified" by the news. And he asked if civil servants consulted colleagues in the Foreign and Commonwealth Office or Ministry of Defence to determine what the chemicals could be used for.

Cable admitted that licences were granted to sell the chemicals for use in the manufacture of "aluminium showers, windows, etc". But he admitted that they "could also be used as precursor chemicals in the manufacture of chemical weapons". He refused to publish additional details, citing "commercial sensitivity".

The chemicals never left the UK as the European Union imposed tough new sanctions on Bashar al-Assad's regime and the licences were revoked later in 2012.

But Docherty has written to Cable demanding to know more about deals with Syria, writing: "How many licences for the export of chemicals have been issued not only in the period in question but in the wider period since the start of the Syrian civil war?"

Commenting on the reports, which were first published in the Sunday Mail, Labour's shadow business secretary, Chuka Umunna MP, said: "The chair of the joint intelligence committee confirmed last week that their assessment was that the Syrian regime had used lethal chemical weapons on 14 occasions from 2012. There are, therefore, very serious questions to answer as to why, in January 2012, export licences for chemicals to Syria which could be used in the manufacture of chemical weapons were approved.

"It will be a relief that the chemicals concerned were never actually delivered. But, in light of the fact the Assad regime had already been violently oppressing internal dissent for many months by the beginning of 2012 and the intelligence now indicates use of chemical weapons on multiple occasions, a full explanation is needed as to why the export of these chemicals was approved in the first place. This is important if confidence in the export licence process is to be maintained."

The Department for Business, Innovation and Skills did not respond to a request for comment.