He urged for new legislation to enable donors to get immediate tax relief on gifts, and to encourage more planned giving, as occurs in the US.
Joffe was speaking in the House of Lords on the 25 per cent decline in giving in the past decade, which the campaign that winds up later this month was set up to reverse.
He contrasted the stinginess of Britain's super-rich with the generosity of the country's poorest 50 per cent, who give more than three times as much as a proportion of their income as the well-off.
"Although the richest 1 per cent of the UK population now own around one quarter of the marketable wealth, while the poorest 50 per cent own only 5 per cent between them, it is the poorer donors who give a much higher proportion of their income to charity," he told peers last week.
The wealthiest 1 per cent of households give an average of 0.7 per cent; the poorest 50 per cent give 3 per cent.
Joffe proposed a non-compulsory benchmark set at an average of 1.5 per cent of annual income, rising to 2 per cent for the very wealthy and tapering to virtually nothing for the very poor. The overall target should be to double giving over the next 10 years, he said.
However, Joffe said that the key players in getting people to give were the charities themselves.
"They must face up to the challenge of proving to donors that they are making a real and positive difference to society, that they are efficient and effective and that they value the support of those who contribute to their work."
He added that charities should not be afraid to ask for generous donations from the wealthy. Also, donors should be shown the positive effects of their giving on beneficiaries to encourage them to give more.
He praised the US example of payroll giving - with almost one-third of employees using this method to give, compared with only 2 per cent in the UK.
Joffe's own charitable trust donates £400,000-£500,000 each year to good causes.
He told Third Sector that the Giving Campaign had "started to move things in the right direction, but there is a long way to go".