An MP has urged the work and pensions secretary, Amber Rudd, to make the benefits system more humane over Christmas by reinstating a long-standing £10 extra payout and returning to a previous pause on sanctioning claimants over the festive period.

The SNP’s Hannah Bardell said Rudd, who pledged last week to make sure the social security system helped people when they most needed it, should act on her words and do the “decent and right thing”.

In a letter to Rudd, she highlighted the decision to partially scrap the £10 Christmas “bonus”, in place since 1972 for many people on benefits. It will not be paid to those receiving universal credit, the new, combined system for working and unemployment payments.

While the sum was small, Bardell wrote – it has been unchanged since 1972 – it was “the difference between some people eating and not”.

She also demanded a reinstatement of a traditional pause over the festive period of sanctioning claimants, in which their payments are docked or stopped as punishment for alleged failures to comply with jobcentre rules.

The Department for Work and Pensions (DWP) has told Bardell this has not been a national policy since 2010, but she wrote that a senior department official had told her it had only been scrapped in 2014.

Bardell told the Guardian the official told her that when the policy was first ended, her office “had to send members of staff home on Christmas Eve very, very distressed because they’d had to sanction people over the Christmas and new year period, and the people they were sanctioning were massively distressed”.

Bardell said: “It caused a huge amount of upset among staff, and really damaged morale.”

Reports have concluded that the sanctions system is ineffective in getting jobless people into work, and tends to have disastrous effects on people’s welfare.

In the letter, Bardell said Christmas was a difficult time anyway for people in poverty. She wrote: “It is completely and utterly morally unjustifiable and totally heartless to cut people’s benefits at Christmas time.”

Rudd sent an open letter to her fellow Conservative MPs last week, promising to take a new approach in her job, which she began in November.

Rudd said she wanted a benefits system “that gets help to people when they most need it, represents the best of British values and has women and children at its heart”.

Bardell said the decision to push ahead with ending the £10 payments and sanctioning claimants over Christmas was completely contradictory to this stated intent.

“At the very least, having a pause around Christmas is the decent and right thing to do,” she said. “It’s not a huge ask. It’s not going to cost them any money. It’s just the right thing to do. People will still be sanctioned in the new year.

“But at a time when there’s so much uncertainty over Brexit and so much damage done by the benefits system, if she really wants to live by the mantra she’s trying to set out, this would be a really positive, decent that she could thing. It’s about deeds, not words.”

A DWP spokeswoman said people on universal credit who also receive other benefits, such as personal independence payments, will still get the £10.

She said: “Sanctions are only used in a very small percentage of cases and work coaches take people’s personal circumstances into account. Universal credit claimants have never received a one-off December payment, but many disabled people on universal credit will be better off on average by £100 month than when they received ESA.”