Plagiarism accusations against Tourism Minister Lindiwe Sisulu were "ridiculous", her spokesperson said on Thursday.

Sisulu's spokesperson, Steven Motale, denied that the tourism minister committed plagiarism, despite penning an opinion piece in which a large section was almost identical to a speech given by former UK attorney-general Dominic Grieve.

Sisulu was responding to criticism around the article she wrote tackling the judiciary. In the article, Sisulu wrote that "mentally colonised" black judges had "settled with the world view and mindset of those who have dispossessed their ancestors". She received backlash from several quarters, including acting Chief Justice Raymond Zondo and African National Congress (ANC) veteran Mavuso Msimang.

The ANC has since distanced itself from Sisulu's comments.

In response to the backlash, Sisulu penned another article published by IOL on Wednesday. In the article, Sisulu said her comments on the judiciary were "narrowly read".

However, the 2 800-word article featured a 400-word section almost identical to a speech given by Grieve in 2013. The similarities between the speech and Sisulu's opinion piece was first picked up by Gareth van Onselen, a political analyst.

The section quotes philosopher Professor Joseph Raz and distinguished UK jurist Lord Tom Bingham.

Motale denied that any plagiarism had taken place. He said anyone accusing the minister of plagiarism was "stupid".

"Plagiarism is when a person, in writing something, uses the words and thoughts of someone else without giving credit to the original author. Minister Sisulu cited the author, the source, the specific piece and date of publication or court ruling instance. This is the exact opposite of plagiarism," he said.

"Whoever makes this charge is either incredibly stupid or incredibly desperate to smear the minister. He or she is a scandal. Go read the 'plagiarism declaration' every university student must sign for every paper they write. This is completely ridiculous."

Sisulu's article makes no reference to Grieve, despite her phrasing bearing a striking resemblance to his thoughts and writing.

Motale said plagiarism was "not acknowledging another person's work or ideas when you use it in your writings, speeches and other scholarly efforts".

However, he said seeing as Sisulu had attributed the content to Bingham and Raz, it could not be considered plagiarism.

"In an opinion piece, as opposed to a dissertation, that is all that is required and possible. The writer is not expected to clutter an op-ed piece with footnotes to the extent these guys seem to imply," he added.

Motale said using ideas that were common knowledge or generally accepted as fact did not require one to cite a source.

"The writings of Lord Bingham on the rule of law are commonly accepted as the textbook definition of the subject. But the minister cited the sources," said Motale.

"The writings of these authors have been reproduced and discussed in various other publications without any substantive changes being made to their key themes on the rule of law."