Several Londoners also reported, via Twitter, that they had seen thousands of Kiwis drunk - but those on the pub crawl reported having an awesome time and police said they were unaware of any issues.
The pub crawl is one of the highlights of the year for many Kiwis in London, and is attended by thousands.
This year, one of the promoters met the High Commissioner, Derek Leask, and the Metropolitan Police before the event to ensure everything was well organised.
However, Mr Clements, a travel adviser, was appalled at what he saw. "I'm just really ashamed. What was going on was totally disrespectful to New Zealand."
A spokesman for the police said no serious incidents had been brought to their attention.
"There is no suggestion they were causing any problems. I'm sure that as disgusting as that [the misbehaviour] would be, it's not the sort of thing we would be made aware of.
"If there was an assault or arrests then, yes, but general 'bad behaviour' is not something we can really take time to go chasing."
He said Mr Clements' claims sounded like "people who have drunk too much".
"As dreadful as it is ... and I wouldn't want to see such a thing, of course ... it sounds like a usual night out in London for people who should know better."
On the event's official Facebook page, many participants thanked the organisers and said they had had a great day.
"I can't believe I survived the Waitangi Day Circle Line Pub Crawl this year ... What an amazing day," said one user. "Cheers to the police, who were in fine form, and to everybody who make this day so awesome."
Another posted: "Good work guys. Had a great day ... Wanna say a big thanks to all the awesome police we met out and about yesterday who all told us we were a well-behaved bunch."
Last month, Mr Clements wrote on the Facebook page that it was a shame locals and tourists of London would have their first impression of Kiwis performing a haka drunk. "Have fun embarrassing our country."
Yesterday, he said he first noticed the pub crawlers when he took the Tube into central London.
Drunk Kiwis were running along the platforms, hanging their legs over the sides and yelling obscenities.
"People on the Tube were quite scared," Mr Clements said. "We've just had the London riots and when you see that degree of disorderly people, that does frighten people."
He saw people urinating on a police vehicle, and against the back of Westminster Abbey - in front of two "outraged" elderly volunteer workers.
"A participant abused a landlord of The Red Lion Pub as the participant wanted to use his toilet. The landlord explained the pub was closed due to damage from a number of participants who were in the bar earlier."
Mr Clements said the behaviour was unacceptable. "I'm not an old prude sitting on my laptop writing letters to the High Commissioner; I get on the booze myself. But I just don't want our country to look bad overseas."
He said he did not want to see the pub crawl banned, just more controlled. "It is not a day that should be represented by drunk Kiwis wreaking alcohol-fuelled havoc on the streets of London, and it does nothing for the image of NZ internationally."
A number of others also voiced disgust on Twitter. One wrote: "Group of Kiwi guys really representing NZ well. So f****** wasted on a Waitangi Day pub crawl they just wet themselves outside Subway. Class."
Another wrote: "1000s of drunk Kiwis on the loose."
High Commissioner Leask did not respond to the Herald yesterday but last month he met Clint Heine, who runs the Facebook page offering expats information on the event.
On his blog, Mr Heine wrote they had had "a cup of coffee and a chat".
Last night, he said he received advice "that we try and behave ourselves as much as we can".
Mr Heine also met the police before the crawl and posted on Facebook: "They have let me know that our presence is an event the police look forward to not just observing, but also participating in. Many police are also trying to learn the haka in time ... They have already done all the planning regarding blocking off the area for the haka and have police allocated (many who jumped at being involved)."
