Protesters gathered outside the Chinese embassy in west London today to callfor a ban on the country's booming trade in ivory from elephant tusks.
Chinese demand for ivory is claimed to be driving the slaughter ofan estimated 40,000 African elephants every year.
With the animals in danger of extinction, wildlife charities are asking China to ban the ivory trade, destroy all its ivory stocks and close ivory carving factories.
Ornaments made from ivory are a traditional symbol of wealth and status in China.
A spokesperson for the Mayor of London has defended criticism of the cost of Mr Johnson's October trip to China claiming the "costs have already been reimbursed many times over" in investment and trade deals.
“The costs of the Mayor’s trip to China have already been reimbursed many times over in terms of deals announced by businesses he met and lobbied on the visit that will provide hundreds of millions of pounds of investment in London," a spokesperson for the Mayor of London said.
"Those deals are part of a huge wave of Chinese investment and confidence in the capital. The objective of the Mayor’s visit was to position London as the city of choice for Chinese business, tourists, entrepreneurs and students with a view to attracting the jobs and growth to London
"The objective of the Mayor’s visit was to position London as the city of choice for Chinese business, tourists, entrepreneurs and students with a view to attracting the jobs and growth to London that are already in evidence in the deals announced since the Mayor returned."
Boris Johnson's October trade mission to China was just another trip "for Boris and his boys club to make deals with the super-rich for the super-rich", Baroness Jenny Jones has said.
Mr Johnson's trip to China in October cost over £65,000 as the Mayor attempted to attract fresh investment to the capital.
"This is yet another trip for Boris and his boys club to make deals with the super-rich for the super-rich," Baroness Jenny Jones, Green member of the London Assembly, told HuffPostUK.
"The Mayor has encouraged Chinese businessmen to buy up homes and even a chunk of Crystal Palace Park, widening the power and wealth gap between the wealthiest and the vast majority of Londoners.”
A spokesperson for the Mayor defended the cost of the trip, claiming London has benefited from numerous investment deals as a result.
London Mayor Boris Johnson's trade trip to China cost over £65,000, a Freedom of Information Request has revealed.
The total cost of the week-long trip was £65,653.42, during which the Mayor held meetings with companies and politicians in a bid to attract investment to London.
Over £50,000 was spent by City Hall on travel, with £1,456 on eight business class train tickets, £11,532 on accommodation, £2,645.92 on incidental expenses and £1043 on visas, the Huffington Post reported.
The Mayor took nine City Hall officials, eight business representatives and seven journalists for the trip.
Boris Johnson has welcomed news that Chinese mobile gaming company Rekoo is opening a London office as he continues his six-day trade mission to promote business and investment.
It will be the first mainland China firm to move to the Tech City cluster, based around Silicon Roundabout in Old Street.
Rekoo says it will initially hire 10 employees and expects to have 25 based in London within three years.
The Mayor of London has visited the 'forbidden city' in Beijing as part of his official trade tour of China. Boris Johnson is hoping to encourage billions of pounds of investment in the capital from Chinese businesses.
One such company is ABP, which is redeveloping the capital's Royal Albert Dock. Today the firm's boss told ITV News that the money coming from China was good for British society. Our China Correspondent Angus Walker reports.
Boris Johnson celebrated an agreement for British designer Thomas Heatherwick to build two Beijing underground stations by taking a trip on the network himself. London's Mayor said Britain remained competitive internationally in creative industries, like design and fashion.
Thomas Heatherwick, who designed the cauldron that featured in the London 2012 Olympics opening ceremony, could also be commissioned to build an entire line for Beijing's underground, which could include 15 to 20 stations.
The Mayor of London continues his six-day trade mission in China today in a drive to encourage closer business links with the UK capital.
It's Boris Johnson's first visit to the country since the Beijing Olympics in 2008.
China is now the world’s second largest economy, worth an estimated $8.2 trillion.
Chancellor George Osborne has said there will be a "streamlining and simplifying" of the visa system for Chinese nationals to head to the UK as he attempts to strengthen business ties with China.
He and London Mayor Boris Johnson have been touring Beijing and meeting with business leaders in an attempt to profit from China's interest in Britain and its culture and industry.
ITV News' China Correspondent Angus Walker reports from the city:
Chancellor George Osborne told students at Peking University that investment in each other's countries should not be seen as a threat but a great opportunity.
Boris Johnson reiterated this view telling ITV News that international investment should be encouraged.