While Mr Darling promised no existing benefit claimants or beneficiaries would be affected by any of his proposals, he indicated that an element of means-testing or taxing could be introduced in the future.
"We want a system that reflects our overriding principle of welfare reform. Today women who lose their husbands get help. Men losing their wives, sometimes with growing children, don't ... no one can tell me the present system provides the right solution.
"If we were starting out today, no one would design a system like this. This is not a sensible use of money, this is not an effective use of money," Mr Darling said during a speech to the Fabian Society.
The system provides a tax-free pounds 1,000 lump sum to women whose husbands die, plus pounds 74 a week for a widowed mother with one child, with pounds 11 for every other child. Widows over 45 get up to pounds 64.70 a week.
But Mr Darling appeared to rule out extending the benefit to all men, because it would cost about pounds 250m and be paid to some well-off people.
"Men without children, some with good salaries, with substantial capital, would get an extra pounds 64 a week. At the other extreme, we could abolish the lot - something I have never considered reasonable," he said.
The Government's reforms would ensure people losing a wife or husband got immediate help with pressing financial worries, such as funeral costs and unpaid bills, and time to "rearrange their lives" after bereavement, Mr Darling added.
He also underlined the need to reform long-term sickness and disability benefits, which he said, were outdated and complex. A quarter of men aged between 60 and 64 received incapacity benefit, which the Tory government had used as "an early retirement scheme" in the 1980s, Mr Darling said.
He added: "Nobody will be forced to work but where someone can work, perhaps with some assistance, we need to make sure he or she can do so."