Some Canadian internet providers are promising high-speed services they aren't always delivering, a CBC Marketplace investigation has found.

"We're totally being pushed on speed," said Dali Bentolila, a telecom consultant from Canada who spends most of his time in Buenos Aires.

Consumers may be swayed by promises of high-speed delivery in promotional material — like advertisements that promise speeds of up toseven megabits per second — but Bentolila says they should beware of the fine print.

"They have to say 'up to' because most of the time it's not the case, so they have to protect themselves," he said.

"I think there are some cases where they can offer those speeds, so they get to put that number out there, and in those cases where they can't offer those speeds, well the 'up to' protects them," he said.

CBC Marketplace also found some Bell customerswere not receiving the top speeds advertised. In some cases, consumers were getting less than 30 per cent of the maximum speed.

Charlotte Burke, Bell's senior vice-president of consumer internet services who is based in Toronto, said the company is upfront in telling consumers of its "up to" service. She said the company is investing millions of dollars in upgrades.

"The substantial majority of our customers' line capabilities are capable of supporting the higher end up of the 'up to' speeds in each of the categories that we actually market," she said.

The consumer watchdog program, which airs Wednesday night at 7:30 p.m. ET (8 p.m. in Newfoundland), also conducted a speed test between Bell, Rogers, Shaw and Telus.