ED Miliband has repeatedly refused to endorse the personal decision by Anas Sarwar, the deputy leader of the Scottish Labour, to send his son to private school.

The UK Labour chief, who has made a point of sending his own son to state school, suggested it was a matter for the Glasgow Central MP.

While he defended the general right of parents to pay for private education, Miliband repeatedly chose not to defend the specific decision of Labour's Scottish deputy.

The Sunday Herald revealed in January how Sarwar had snubbed the Labour-run primaries used by his constituents and instead chosen £8234-a-year Hutchesons' Grammar for his son. The decision is understood to have gone down badly with senior party members.

Sarwar is himself a former pupil of Hutchesons' Grammar, in Glasgow's southside, and recently gave a talk there to S4 and S5 students.

In 2010, comprehensive-educated Miliband announced he would send his son Daniel, then 15 months old, to a state school in London.

He said of parents who chose private school: "I'm not angry at them but I think it would be better for our society if they felt they were able to send their kids to state school."

Speaking to the Sunday Herald in Edinburgh on Friday, Miliband confirmed he had kept his pledge and Daniel was having a state education.

Asked what message it sent out when Sarwar sent his son to a private school, Miliband said: "Look, parents have to make their own decisions about the schooling of their kids. I made my decision about what was best for my kid, but I'm not going to start getting into criticism of other colleagues when they make their own decisions."

When it was pointed out that Sarwar had turned his back on schools effectively run by Labour, which controls Glasgow City Council and where the husband of Scottish Labour leader Johann Lamont is depute leader, Miliband said: "I've given you my answer." Asked if he would defend Sarwar, he again said: "I've given you my answer."

Asked why he wasn't defending Sarwar, an increasingly uncomfortable-looking Miliband said: "I absolutely defend the right of parents to make their own decisions about their kids."

Finally, when it was suggested that Sarwar, who has spoken often of his commitment to social justice, was a hypocrite, Miliband said: "I think I've answered your question."

Sarwar, 31, a dentist before entering politics, became MP for Glasgow East in 2010. The seat had previously been held by his father, Mohammad Sarwar, the UK's first Muslim MP, now Governor of Punjab in Pakistan.

Tipped as one of the stars of Scottish Labour and a potential leader, Anas Sarwar became Lamont's deputy in December 2011.

However, the decision to send his five-year-old son to "Hutchie", where fees range from £8234 a year for primary to £10,230 for secondary pupils, has proven controversial.

He has been accused of double-standards for talking about the need for "world-class public services" and tackling inequality while choosing an elite institution for his family.

Hutchie pupils achieve better grades than children at local comprehensives while fewer than 5% of Scots children are educated in the private sector.

Since the Sunday Herald revealed Sarwar's decision, he has been sidelined from his party's pro-Union effort in the referendum. He was the original leader of the party's "United with Labour" campaign, but Lamont recently elbowed him aside. He is now going round Scotland on a bus.

Nationalist MSP John Wilson said: "Clearly, questions must be raised about the continuing role of Anas Sarwar as deputy leader of the Labour Party in Scotland when even Ed Miliband is not prepared to defend his decision to send his son to a fee-paying school. This highlights the growing division within the Labour leadership."

A Scottish Labour spokesman said: "This is a new low for the SNP. The Labour Party ... are united behind our campaign to keep Scotland strong in the United Kingdom. The SNP look increasingly desperate as they bicker about their failing campaign strategy and who will replace Alex Salmond after a No vote. Most Scots can see through these lame attempts to divert from the crisis they are in."