HOLYROOD'S combination of constituency and regional MSPs could be ended under plans due to be debated by the SNP.

Members have tabled a motion for the party's conference in October calling for future elections to be fought under the fully proportional single transferable vote system (STV).

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The move would end the present hybrid system which elects two kinds of MSP, with 73 of the 129 representing constituencies and the remaining 56 in eight electoral regions.

Supporters say switching to STV would be simpler for voters, who face different systems in Holyrood, Westminster, European and council elections.

They also say it would make the parliament more accountable to voters because all MSPs would have to win a personal mandate from the electorate.

At present, voters pick a party to represent them in the regional vote. Individual candidates appear on lists controlled by the parties under what is known as the "additional member" system.

The motion has been submitted by the Aberdeen South and North Kincardine constituency association and has been included in a draft conference agenda seen by The Herald.

MaureenWatt, the MSP for Aberdeen South and North Kincardine and

public health minister in the Scottish Government, said the call had come from grassroots members, though she was also personally sympathetic to making the change.

She said: "I think we have moved on from 1999 when Labour and the Lib Dems viewed regional MSPs as second class MSPs, and I think people now know that have not one MSP but eight.

"But I've always believed we should look at reform of the voting system."

The present system has been used since the creation of the parliament in 1999, though constituency boundaries have been redrawn since then.

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The new Scotland Act gives Holyrood control over the election process, which was previously reserved to Westminster.

The conference motion states that "implementing STV in Scottish elections would remove an element of complexity from Scottish elections by reducing the number of electoral systems, help to raise turnout and ensure all MSPs must win a personal mandate from voters".

It does not set out the new system in detail.

However, an STV parliament would probably require more but smaller constituencies or a multi-member constituencies, similar to council elections.

It is unclear whether STV would give the SNP and electoral advantage compared with the present hybrid arrangement.

In the last Scottish election in May, the party secured 63 of Holyrood's 129 seats - 49 per cent of the total - after winning 47 per cent of the constituency vote and 42 per cent of the regional ballot.

The party won its 59 constituency seats by such large margins it was able to pick up only four regional seats across the whole of Scotland.

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Five years earlier, then-leader Alex Salmond won 69 seats - 53 per cent of the total - with 45 per cent of the constituency vote and 44 per cent of the regional vote.

Gaining an outright majority under those circumstances was widely seen as "breaking" the semi-proportional Holyrood system.