NDP Leader Thomas Mulcair says Prime Minister Stephen Harper should be doing more to help two Canadians who have been jailed in Egypt for more than six weeks without charges.

Mulcair鈥檚 comments come one day after it was announced that John Greyson and Dr. Tarek Loubani will be held for an additional 45 days in Cairo鈥檚 notorious Tora prison.

Foreign Affairs Minister John Baird said he raised his concerns about the Ontario men鈥檚 imprisonment with his Egyptian counterpart late last week.

On Sunday, the Prime Minister鈥檚 Office weighed in on the case for the first time since the pair鈥檚 arrest, saying in a statement that in the absence of charges against Greyson and Loubani, the two should be released 鈥渋mmediately.鈥

Mulcair said Monday that while he鈥檚 pleased the PMO raised the issue, he鈥檚 calling on Harper to do more.

鈥淣ow it鈥檚 time for action,鈥 he told reporters in Ottawa.

鈥淚 think Mr. Baird, in the limits of his mandate, has been able to act appropriately. Now it鈥檚 up to the prime minister take it up to another level and that鈥檚 what we called upon Prime Minister Harper to do last week.鈥

Cecilia Greyson, John Greyson鈥檚 sister, said she鈥檚 grateful for the strongly-worded statement from the PMO, which she said: 鈥淚ndicates the level of concern that the Canadian government has around this case.鈥

鈥淐ertainly the Ministry of Foreign Affairs has been very active in the case since the beginning and to have the prime minister issue a strong statement really gives us some hope, certainly, that the Canadian government is behind us,鈥 Cecilia told CTV鈥檚 Canada AM.

Cecilia said she hopes Harper will be able to talk to Egyptian interim Prime Minister Hazem el-Beblawi, and 鈥渉opefully push for a release.鈥

Greyson and Loubani were arrested on Aug. 16 in Cairo, where they arrived with transit visas on their way to Gaza. The unrest in Egypt prevented them from crossing the border and they were arrested after helping the wounded during one of Cairo鈥檚 violent protests.

In a , the men explained the circumstances surrounding their arrest and described 鈥渞idiculous鈥 conditions in the Tora prison. They said they鈥檙e sleeping with cockroaches on the concrete floor of a crowded cell and drinking from a 鈥渟ingle tap of earthy Nile water.鈥

In protest, both men began a hunger strike on Sept. 16.

Cecilia said the men鈥檚 families and lawyers have provided 鈥渁mple documentation鈥 to prove that the pair was simply travelling through Egypt in August, but the prosecutor has 鈥渟hown no interest.鈥

鈥淲e鈥檙e really treating this as a human rights issue right now,鈥 she said.

Cecilia Greyson had previously said she believes the Egyptian government has "political motivations" for keeping her brother and Loubani in jail, because the men witnessed numerous deaths during the Aug. 16 protest.