A memo from a Downing Street source suggesting Britain would refuse to work with EU countries who accept a delay to article 50 should make the government “ashamed”, a former cabinet minister has said.

The note, sent from a No 10 insider to the Spectator magazine, also sets out how the government plans to “scupper” the Benn act that blocks no deal, threatens that the duty to cooperate with the EU will be “down the toilet” if there is a delay and points clearly to the increased likelihood of a no-deal Brexit.

It also describes the British parliament as being “as popular as the clap”.

Amber Rudd, the former work and pensions secretary, who left the parliamentary Conservative party to become an independent MP, said she believed the note, which was not denied by N0 10, will have come from Johnson’s powerful adviser Dominic Cummings because of the language in it.

Speaking to BBC Radio 4’s Today programme, Rudd said: “It sounds angry and desperate and the language that is used I do not believe should be the language of a UK government.

“Since it hasn’t been denied by No 10 … one can only assume it’s come from the centre, from the prime minister’s adviser, and the style of it seems to imply that [of] Dominic Cummings, otherwise it would have been heavily denied and heads would have rolled.

“It reveals that there doesn’t appear to be an actual plan at all. Instead, what they are doing is angrily, apparently, begging the EU not to support a delay that will be required because of the decision that parliament has taken.

“I would urge the prime minister to take control of this and give us some clarity, dignity and diplomacy on what is taking place.”

It is unclear whether the view in the memo reflects the wider view of cabinet and other staffers, as divisions remain between the vote leave contingent at No 10, led by Cummings, and the more moderate voices from the ex-city hall staffers who worked for the prime minister when he was mayor of London.

The transport secretary, Grant Shapps, sought to play down the 400-word memo on the Today progamme, saying the source of it was unknown.

Asked if the UK would withdraw cooperation with EU countries if they sanction a Brexit extension, he said: “No, I don’t think that’s the case at all.”

The note said: “Supporting delay will be seen by this government as hostile interference in domestic politics, and over half of the public will agree with us.

“They think now that if there is another delay we will keep coming back with new proposals. This won’t happen. We’ll either leave with no deal on 31 October or there will be an election and then we will leave with no deal.”

In a direct challenge to Brussels, the memo said: “Those who supported delay will face the inevitable consequences of being seen to interfere in domestic politics in a deeply unpopular way by colluding with a parliament that is as popular as the clap.”

Rudd suggested Johnson did not have a plan but instead was begging Brussels not to countenance a delay.

She said: “I don’t think this will have any impact at all except make everybody slightly ashamed of the position the UK government appears to be taken.”

Defence and security are two of the areas in which the UK might stop cooperating with the EU if there is a delay to Brexit, according to the memo.

“Those who support delay will go to the bottom of the queue,” it said.