A 2-year-old New Zealand boy and his Indian-born mother were barred from India and, on their return to Auckland, delayed for four hours and questioned after their names appeared on a terrorism blacklist.

After a 20-hour journey to New Delhi, Shubhneet Kaur, a New Zealand citizen from Manukau, and her son, Bachint Vir Singh, were turned back to New Zealand despite holding valid tourist visas for India.

They pair arrived back in Auckland three days after their Monday evening departure - only to face a Customs interrogation about why they were on India's list of possible terrorists.

"My wife and baby boy were treated like criminals," said Ranvir Lali Singh, a builder, justice of the peace and secretary of the Auckland Sikh Society.

"My son is just a 2-year-old baby and my wife is a housewife.

"It is so ridiculous to even suggest they can be terrorists or pose a threat to India's security."

In Auckland, Mrs Kaur was repeatedly questioned by several people about why she and her son were denied admission into India, and every item of her luggage was searched.

Despite pleas from Mr Singh from the arrivals lounge for the toddler to be released to him, the boy was kept with his mother throughout her ordeal.

Mrs Kaur walked out of the Auckland Airport arrivals hall in tears and was too distraught to speak when approached by the Weekend Herald.

The 35-year-old has lived in New Zealand for 12 years and has been a citizen since 2003. Bachint was born in New Zealand in August 2007.

Their trip to India was meant to be a one-month holiday during which they were to attend a relative's wedding and visit the little boy's sick grandmother.

"They have done absolutely nothing wrong, and how they have been treated is inhumane and unfair. This will not be the end of it," Mr Singh said.

"If their names are really on India's watchlist, why did the Indian High Commission issue tourist visas for them to go to India? Wellington should have already picked that up if it was true."

Mr Singh said he would lodge a formal complaint with the high commission and ask Labour Party foreign affairs spokesman Chris Carter, a former Minister of Ethnic Affairs, to raise the issue at a diplomatic level.

Yesterday, Mr Carter, who knows Mr Singh and Mrs Kaur, said he would be asking the Indian High Commissioner for answers at a meeting on Wednesday.

"I could not imagine that they could be involved in any Sikh extremist activities, and I suspect it is a name similar to theirs that was on the India list."

Mr Carter said he was angry with the Customs Service over the way it had treated the two New Zealand citizens.

But a Customs spokesman said the Auckland delay had been caused by several factors including language issues, changing of shifts for officers and delays in checks and processing.

The Indian High Commission in Wellington said it was unaware of the incident.

A spokesman said the India blacklist was of "undesirable persons", including terrorists and those who had been involved with unlawful activities.

"This may be a case where our list does not match with the one in India."