The society supports the Bill, which would give terminally ill people the legal right to choose whether a doctor can assist in their suicide, while the commission opposes it.
The commission told the select committee that more needed to be done to ensure disabled people have access to services to allow them to live independently, before any rights to die are increased. But the society says the commission's opposition to the Bill is inconsistent with a survey it conducted of 91 disabled people in 2002.
Mark Slattery, the society's head of communications, said the poll showed 60 per cent of those consulted thought there should be new laws to make euthanasia or assisted suicide possible. The Commission published the results online, but removed them within a month. Slattery said the commission did not mention this survey when it gave evidence to the select committee.
He accused the commission of "removing the poll and covering the traces".
Liz Sayce, the commission's director of policy and communications, denied this, but admitted the poll was not included in the evidence. There was a "deep split" on the need for laws sanctioning assisted dying, she said.
"At the time of the poll, we held an open debate with the Voluntary Euthanasia Society on whether euthanasia or assisted suicide should be introduced," said Sayce. "Having heard a full exploration of the arguments, the audience moved their position, and the large majority were against change in the law." This information was included in the commission's evidence to the committee, she said.
The society funded a YouGov poll published last week, which showed that 80 per cent of disabled people supported the bill. Slattery said the commission should have conducted a larger version of its earlier survey before forming its submission to the committee.
But Sayce contended: "Instant polls of existing public opinion are a clumsy tool in relation to issues of such complexity as this."