Warning that millions of people already in debt are being left with "nothing to fall back on", Dr John Sentamu called upon minister to reduce the time period.
Writing in the Sunday Times, he said: "In the Bible, the hardest-pressed of all poor people were summarised as 'widows and orphans' for they were the group most at risk and with least support.
"Our concern should be for their present-day successors whose essential outgoings are costing more and more and their incomes standing still or going down.
"They fear Universal Credit, particularly because it seems to assume that everyone has a nest egg which will tide them over as they wait a minimum of 42 days for payouts.
"That is grotesquely ignorant, for millions of people, especially those in need of support, are already in debt and have nothing to fall back on."
Claiming the six week wait is fuelling evictions, rent arrears and rising levels of debt, critics say the wait should be reduced to four weeks.
In the House of Commons on Wednesday, the Prime Minister dodged a Tory revolt over the issue by pledging to scrap charges of up to 55p per minute to call a Universal Credit helpline.
Conservative MP Stephen McPartland, who has threatened to rebel over the roll-out of Universal Credit, suggested opponents were "very, very close" to achieving a "resolution", though the Government insisted no changes were imminent.