Official data do not include emissions from making imported goods but both sets of researchers say they should.
The Proceedings of the National Academy of Sciences reports 26% of global emissions come from producing goods for trade.
The Carbon Trust found such "embedded" CO2 could negate domestic carbon cuts planned in the UK up to 2025.
Researchers want all nations to publish their data on embedded emissions.
Glen Peters of research group Cicero, lead authors of the PNAS report, told BBC News: "There is a degree of delusion about emissions cuts in developed nations. They are not really cuts at all if countries are simply buying in products they used to manufacture.
"We really need all countries to be developing and publishing the full extent of their emissions, whether they are produced domestically or outsourced through traded goods."
The issue of embedded (or outsourced) carbon emissions has been recognised for several years, and the methodology to track emissions pathways is developing.
Cicero produced a trade-linked global database for CO2 emissions covering 113 countries and 57 economic sectors from 1990 to 2008.
It found that emissions from producing exported goods increased from 4.3Gt (gigatonnes) of CO2 in 1990 (20% of global emissions) to 7.8Gt of CO2 in 2008 (26%).
Most developed countries increased their consumption-based emissions faster than their territorial emissions - particularly from goods such cars and clothes.
The Carbon Trust research confirms that the UK has increased emissions since 1990 rather than decreasing them, as politicians typically claim.
What may alarm ministers even more is a projection that the radical CO2 cuts planned by government into the 2020s may be offset by ever-increasing levels of CO2 in imports.
Dr Peters said: "Publishing this sort of data is the first step. The next step - what to do about it - is more difficult.
"It raises questions about consumption patterns, and whether countries should consider border taxes on imports from countries with no controls on CO2 emissionsâ€¦ though this is controversial and will be some way down the line."
A UK think tank, the Public Interest Research Centre (Pirc), has been discovering how uncomfortable this issue is proving for rich nations.
A succession of Freedom of Information requests reveals a degree of frustration among some British civil servants that the UK insists on basing its emissions calculations solely on domestic emissions.
One piece of government correspondence reveals: "While technological efficiency has improved the CO2 impacts of our products since 1992, the rise in UK consumption has outstripped the improvements achieved.
"The government needs to be cautious about over-claiming on its achievements in decoupling economic growth from environmental degradation."
Ministers are well aware of the issue, but insist that the UK should stick to reporting domestic emissions, as these form the basis for international climate negotiations.
They also point out that emissions data from major exporters like China is notoriously opaque, and that the methodology for calculating outsourced emissions is unreliable. They say all this creates even greater pressure for the UK to persuade China to cut its own emissions.
Guy Shrubsole, from Pirc, told BBC News: "This is a cop-out. The figures aren't perfect but the problem has been recognised for several years and the calculations are getting better all the time. In the UK our emissions are up - not down.
"Of course China needs to be part of a global climate agreement. But for a government which wants to be the greenest ever and is committed to data transparency it's essential that the British government publishes the best data available right away - and then figures out what to do about it."

The Sussex academy wicketkeeper played for Jersey Under-19s in the Netherlands earlier in the year but has never appeared for the senior side.
Opening batsman Dean Morrison, whose ineligibility for the island this summer was due to the amount of time he had spent overseas, is also selected.
The annual 50-over match takes place in Guernsey on 7 September.

The former Deputy Chief Constable was confirmed in the top job at a meeting of Strathclyde Police Authority in Glasgow on Monday.
The post vacated by Mr Corrigan will now be filled by former Assistant Chief Constable Rhuaraidh Nicolson.
In turn, his position will be filled by Chief Superintendent Russell Dunn.
Mr House was appointed last week to head up Scotland's new single police force, which comes into being in April next year.
He has already said that as many as 3,000 support staff could be lost as he seeks to merge eight forces into one.
The extent of carbon dioxide (CO2) emissions "hidden" in imported goods is growing, according to two studies.
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Jersey have named 15-year-old Jonty Jenner in their squad for next week's inter-insular game against Guernsey.
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Campbell Corrigan has been named acting Chief Constable of Strathclyde Police following Stephen House's appointment to head Scotland's new single force.