According to a letter obtained by CTV News, “advances in technology” is the reason that most adults with diabetes now don’t qualify for a disability credit that can reduce their tax bills by as much as $1,500 a year.

In the July 31, 2017 letter, Revenue Minister Diane Lebouthillier explained that in order to receive a disability tax credit under the Income Tax Act, one must “require life-sustaining therapy (LST) at least three times each week for a total period averaging at least 14 hours a week to sustain a vital function.”

“In the case of portable devices like insulin pumps, the time that the device takes to deliver the therapy does not count toward the 14-hour requirement,” Lebouthillier added in the letter. “Activities like following a dietary restriction, exercising, traveling to receive therapy, going to medical appointments, shopping for medication, or recuperating after therapy do not count towards the 14-hour requirement.”

A leading reason for people with diabetes losing their special tax status, the letter suggested, are modern, portable insulin pumps.

“In general, and with consideration given to recent advances in technology, adults who independently manage their insulin therapy on a regular basis are unlikely to meet the 14-hours-per-week requirement,” Lebouthillier wrote.

According to Diabetes Canada, as many as 150,000 Canadians now stand to lose their disability tax credit under the Liberal government’s current interpretation of the Income Tax Act, which seems to have been adopted early this year.

“Diabetes sufferers have been eligible for the disability tax credit for over a decade, but now this government is stripping it away and raising taxes by over $1,000 on these vulnerable Canadians,” Conservative MP Pierre Poilievre said during Question Period on Monday.

To which Lebouthillier replied, “Our government is committed to ensuring that all Canadians have access to the credits and benefits to which they are entitled."

The issue has put the government on the defensive over taxation yet again after having recently scaled back proposed changes to the way small businesses are taxed and backpedaling from a CRA plan to tax employee discounts -- a move that would have disproportionality affected lower-income workers.

“The Liberals have no idea what's going on within the CRA which would be the second time within a month,” NDP MP Nathan Cullen told reporters on Monday. “Or this is an intentional policy change that they're just not being honest with about.”

The opposition is now challenging the government, saying that the degree of one’s disability should be determined by their doctors -- and not bureaucrats. Lebouthillier has promised to meet with diabetes groups this week to discuss their concerns.

"More and more people are very concerned,” Juvenile Diabetes Research Foundation president and CEO David Prowten told CTV News on Monday, “because obviously it’s a very expensive disease and this credit's being taken away from them."

With a report from CTV News senior political correspondent Glen McGregor

Letter from Revenue Minister Diane Lebouthillier by CTV News on Scribd