The firm said that the UK economy had been surprisingly strong in 2013 and tipped it to remain so until at least until the 2015 General Election.
Andrew Milligan, head of global strategy, said: "The UK equity position has been raised to Heavy taking account of the better prospects for domestic demand into 2014."
SLI expects growth of 2% to 3% in the UK next year. This matches the assessment of the Office for Budget Responsibility which last week upgraded its growth forecast for 2014 to 2.4%, up from 1.8% in March.
There was a suggestion from SLI that political considerations could help sustain the recovery which has been aided by state schemes such as Funding for Lending, which directs cheap funding at banks.
"Growth has surprised to the upside in two countries in 2013, namely the UK and Japan. In both cases, government policy has proven effective in kick starting an expansion, especially for the consumer; although there is a risk that this begins to fade into 2014-15, the electoral cycle would suggest otherwise," Mr Milligan wrote in the latest Global Perspective paper published by SLI.
Consumer spending has been a key driver behind the recovery in the economy. However, it has been accompanied by rising borrowing, leading to worries about how sustainable it is.
SLI is not alone in linking the UK's economic path to the electoral cycle.
Trevor Greetham, director of asset allocation at Fidelity Worldwide Investment, said yesterday: "The UK is likely to enjoy an old-style housing boom in the run up to the 2015 General Election."
Mr Milligan said that politics could have a major impact on financial markets in the coming year.
"The house view remains confident about the ability of companies to generate positive cashflows into 2014-15," he said.
"Together with current market valuations, this still suggests investors should remain exposed to riskier assets, primarily equity and real estate.
"The bad news is that government decisions, especially about structural reforms but also fiscal policy and regulation, could periodically have a major impact on market sentiment, generating turbulence in the prices of financial assets."
Looking globally, he said that increased consumer demand, particularly for items like homes and cars, is sufficient to lead to businesses rebuilding their inventories.