It was also alleged that the US supplied Iraq with 14 consignments of deadly biological weapons - including anthrax bacteria and a botulism- inducing organism.
The allegations were made last night by Channel 4 News, which said many of the US exports took place after an Iraqi gas attack on the Kurds which provoked international outrage.
Mr Robertson said he understood the antidotes supplied by Britain were exported to Iraq as a medicine and there was no embargo on selling medication to the Iraqis.
He said: "We'll investigate it, but I understand that it probably was exported on the grounds that it was medication and medications are allowable exports today."
Mr Robertson also stressed that, as he understood the situation, the exports took place "long before" Labour came to power last May.
He added that the whole question of exports was a matter for the Ministry of Defence, the Foreign Office and the Department of Trade and Industry.
The programme claimed that American records showed that both Britain and the US had contributed to Iraq's chemical warfare capability they are now determined to destroy.
The programme alleged that the 14 consignments of biological materials were exported by the US to Iraq between 1985 and 1989.
It alleged that when the US eventually blocked an Iraqi order for materials to protect troops against nerve gas, the country turned to Britain which in March 1992 supplied the Iraqis with a nerve-gas antidote.
Mr Robertson was challenged over his statement to the Commons this week that it was now known that Iraq might have large quantities of the Agent 15 chemical weapons when the Allies apparently knew as long as ago as 1990 that Saddam had it.
He replied that the concrete information had only recently come to light. "Last November was the point where we were receiving information on a solid basis that was what he had. We researched that, and the moment I got confirmation, within five days of me getting confirmation, we took that to Parliament and announced it."
On the claim that the Allies were practising double standards about Saddam's chemical weapons, the Defence Secretary declared: "The past doesn't answer the present."
And he added: "Are you genuinely suggesting that, simply because something happened in the past, and he got that capability, we should do nothing now? The reality is that he has got these weapons, the weapons inspectors are being denied the access that the UN has a right to have under international law.
"What we're saying now is, do people want him to get off scot-free, do they want the inspectors to be denied access, do they want him to continue to have that capability?".
He said the Government would like to look into as many of the allegations as possible but stressed that he was concerned about what Iraq had today and what dangers it posed to the world.